Why would a guy be offended if you decide to perform oral sex on him.......but with a condom?

I am a very sexual person but i practice saftey often. I once had a situation with a guy friend who asked me to perform oral sex on him during a night of sex. At first i declined, but with an exception i commanded him to wear a condom while i did it, he was kinda hesitant at first but I guess he didnt want to pass up the opportunity of getting some HEAD so he did it anyway…...............but of course he complained and bitched about it at another time. He said that i treated him like he was NASTYor something. But nowadays you gotta take precautions no matter who it is or how clean a person CLAIMS to be. Because i once developed strep throat from giving my ex- Boyfriend( childs father) oral sex.