Mexican food is part of Mexican culture. That's where people take offense. You wouldn't say for example, 'I don't think she's ugly, I just hate her face.'
It's not about Mexican food, just some common ingredients that you don't like. These are common ingredients prevalent in dishes from all cultures, and people who live in the U.S. are fortunate to have a wide variety of food options-- it's not like there's nothing but Mexican cuisine everywhere you turn.
It's not so much what you're saying but how you're saying it that's offending other people. When in doubt, turn down dinner or lunch or what have you, and let other people enjoy the things that you don't.