In the beginning of cartman’s speech, there’s a possibility that kyle genuinely believed that cartman was actually confessing to him which cause him to panic for a bit. I think kyle deep down knows that cartman has feelings for him
Notice when cartman says “kyle I love you babe” we see that kyle is genuinely surprised and not angry. It’s only when cartman says “when we kiss..” kyle became angry cuz cartman was lying about the kiss +