You would be insulting them if you didn’t wear a kippa. I’m Catholic. If you were to come to a Catholic church and did not dip your index and middle finger in the Holy Water and make the Sign Of The Cross I’d be insulted. Or if you didn’t genuflect in front of the altar.
I recently attended a Catholic funeral.
As I have never been in a Catholic church before, I did not know the proper procedures. Although I’ve seen the sign of the cross made a gazillion times on TV, I have no idea which hand and what direction or which point is made first, etc., etc.,, let alone the rules for the Holy Water. No idea at all what genuflect in front of the alter entails. Sorry if you would be insulted. Sometimes people are insulted by not doing things correctly. Damned if you do, damned if you don’t.