I know many people are saying Kyo should just open up about his past with the kids and let them help but honestly I don't blame him for how he acted.
Breaking their hearts with his words is nothing compared to having them fear for their lives. We know that the kids are capable and can fight, but we must remember that Kyo LITERALLY saw Souji kill two people along with their digimons. Like this is terrifying when compared to what they have dealt with until now.
Also let's not forget that Kyo was against them interacting with KLAY during the tactics arc so it's not so weird that he outwordly decided to force the others to hate him in order to protect them.
IF COUGARMON who until now acted as the voice of reason and reminded Kyo various times that the kids are stronger than he thinks also doesen't try to make him reason more than just asking him if he is sure about his choice, it means Cougarmon himself isn't sure the kids could deal with an enemy like Souji.