Chizkuni (13:3) is among the numerous commentators who suggest that when the scouts were chosen for this mission they still were “kosher,” but as soon as the mission itself started (i.e. from the moment they “went”), they no longer were. [Gur Aryeh (13:3) says that once they were appointed to be the “eyes and ears” of the nation, they were influenced by the people they represented, and their intentions now reflected those of the nation.] By telling us that they were initially “kosher,” we know that the men who were chosen weren’t troublemakers, and wouldn’t have been perceived as such by anyone.
Although this is the most common answer given, it does leave us wondering if, when telling us that the scouts were initially “kosher,” Rashi should have made it more clear that this was only true when they were chosen to go on the mission, but not once they started it. This could have been easily accomplished by merely changing one word, from “and at that time” to “at the time they were chosen,” rather than relying on our trying to reconcile his comments here with his comments several verses later.
It has been suggested that the expression “eitzah ra’ah,” which in this context is usually translated as “bad intent,” really means that it was a “bad idea.” In other words, sending scouts to verify whether the land was good (and conquerable) was a bad idea from the get-go, not just in hindsight after the scouts bad-mouthed the land. If it was just a bad idea, without having any bad intent behind it, there is no contradiction between it being a bad idea from the outset and those who carried it being upstanding individuals. However, Rashi himself, in his commentary on Soteh (35a) explains “eitzah ra’ah” to be their intent to badmouth the land, not the notion of going in the first place. Since we are trying to reconcile how Rashi could say they were initially “kosher” with his saying that the “eitzah ra’ah” was in place when they first went, it would be difficult to use a definition for “eitzah ra’ah” other than his. Besides, Moshe himself thought it was a good idea (D’varim 1:23); how could it be considered a “bad idea” if Moshe agreed with it? And G-d did (eventually) acquiesce to the request (3:2); even if it wasn’t ideal to send them, and He only agreed because the people insisted upon it (see D’varim 1:22), would He have done so despite it being a bad idea? It’s one thing to say that it would have been better not to need to send scouts (trusting G-d instead), but because it was unfortunately needed based on the nation’s spiritual weakness, it’s better to send them than to force the nation to try to conquer the land without knowing what it entails. But if, even after the nation insisted on sending scouts, it was still a “bad idea” to send them, why did G-d agree to it (which is a step beyond allowing it)?
The term “and they went,” which teaches us that their “coming” was consistent with their “going,” is said after the scouts had already returned from seeing the land (Bamidbar 3:25). Although saying “and they went” at this point may be superfluous, on a “p’shat” level it nevertheless refers to their return trip from the Promised Land, not to their trip to the Promised Land to go see it (see Ibn Ezra). Does this change on the “d’rash” level, which the Talmud is working on? Must the trip that the “coming” is compared to be their trip to the Promised Land rather than their trip from it? It is obviously a more profound statement if they had bad intentions even before seeing the Promised Land than if they only had them after seeing it, but can we extend their bad intentions to an earlier time just to make it seem worse? If the point of the Talmudic statement was that even before they returned the scouts planned on doing whatever it takes, even badmouthing the Promised Land, in order to convince the nation not to try to conquer it (so that it was premeditated, as opposed to a spur-of-the-moment decision made after they returned, whether before or after Kalev voiced his opposition), then there is no contradiction between the scouts being “kosher” before their trip but not “kosher” after it. This approach hits a similar roadblock though, as Rashi, in his commentary on the Talmud, is explicit that the “going” refers to their trip to see the Promised Land rather than their trip back after seeing it, making it difficult to use this approach to reconcile the apparent contradictions between his comments on the two verses in Bamidbar.
The verses are explicit that the sin of scouts was their being “motzie dibah” about the land (14:36-37). Radak (Sefer Hasherashim, daled bais bais) and Ramban (13:32) say that “motzie dibah” refers to saying something that is not true, while “mavie dibah” refers to saying something that is true (see B’raishis 37:2), even if damaging. At first, Ramban continues, the officers told the truth, that the land was bountiful, but it’s inhabitants mighty. This concerned the nation, but Kalev’s words reassured them, and they were still willing to go. It was at this point that the lies started, with the officers claiming that the land eats its inhabitants (see Ramban on 14:37), with the lies and exaggerations finally convincing the nation not to go.
Rashi, on the other hand, understands “motzie dibah” to be “propaganda” (14:36-37). While not necessarily a lie, the Old French word Rashi uses means “to slander” (Targum Hala’az). The officers used propaganda (including exaggerations and unproven conclusions) to convince the nation that they wouldn’t be able to defeat the inhabitants. According to Rashi, the Talmud (Soteh 35a) is telling us that the scouts had planned, from the very beginning, to use whatever means necessary to convince the nation to follow their conclusion, even if it means spreading propaganda.
They didn’t go into their mission with any preconceived notion about what their findings would be, and could therefore be considered unbiased (“keshairim”) before it started. Nevertheless, they didn’t plan on just reporting the facts, but imposing their conclusions based on those facts onto others. Instead of trusting the ability of the nation to decide for themselves what to do with the information they were sent to gather, they manipulated the nation to act the way they wanted them to act. I would suggest that this might be the “bad intent” that Rashi says they had from the very beginning, even before they left.
Explaining why the Torah needs to clarify that the “hotza’as dibah” the scouts were guilty of was “bad,” Rashi (14:37) says that “dibah” could be used for good things or for bad things; since this one was for a bad thing, the Torah calls it a “dibah ra’ah.” Nevertheless, the mission the scouts were entrusted with was merely to gather information, not to make any decisions for everyone else based on that information. By deciding to do whatever it takes to convince the nation to follow their conclusions, they had a “bad intent” from the very beginning, even if, regarding their perspective on the Promised Land itself, they were initially “kosher.”