What does it mean when you tell someone your gay and they instantly defend themselves?

I've told friend and family and strangers that i'm gay and rarely has it gone bad or awkward for me. Where i haven't been able to control the situation or handle it. Today i had a thought and then remembered coming out seriously to a best friend years ago and that he instantly defended himself, unlike anyone else to this day. Repeating that "I'm not gay" "I don't like guys" etc for a good 5 minutes.I tried googling for information and other cases and what does it mean. If it was typical negative response, if he thought i liked, had feelings or had a crush on him. Or if it just was the stereotype straight males have of gay friends. "gay guys like all guys" or something like that.Just curious on your guys thoughts and opinions as i couldn't find what i wanted on the internet. Or any information on google and now its bugging me.