What do you mean by Kapoors are Hindus not Punjabis? Punjabi is not a religion. Punjabis are people who originally belonged to Punjab. Are Gujaratis not Hindus? Are Bengalis not Hindus?
Kapoors are both Punjabi speaking and Hindi speaking. Kapoors from Punjab region are Punjabi and there are some Kapurs from UP, Delhi and other areas who are Hindi speaking but mostly Kapoors are Punjabis.