Or HaChaim on Numbers 14:10/אור החיים על במדבר י״ד:י׳

1 ויאמרו כל העדה לרגם אותם באבנים, The whole congregation said to stone them. Why did the people not react in a similar fashion as soon as Caleb said in 13,30: "we can certainly go up and inherit this land?" Presumably the people did not pay any heed to the testimony of a single individual, as such testimony is halachically meaningless when the witness is confronted by two or more witnesses disputing what he said (compare Deut. 19,15). Now that Joshua had joined Caleb, the two represented a valid set of witnesses and the fact that they were outnumbered was halachically irrelevant (compare Makkot 5). In law, the two sets of testimony ranked equally. As a consequence, the two testimonies cancel each other out so that legally speaking the people did not have whom to rely on. Feeling frustrated, the people wanted to kill the witnesses who made up the minority report.

2We also need to know why Joshua and Caleb did not invoke the rule we have just mentioned which would have invalidated the testimony of the ten spies? Perhaps they were afraid that the people would consider Joshua's testimony as prejudiced inasmuch as he was Moses' personal valet ever since his youth.