I will say your parents did a very poor job in trying to discuss their views on the matter. I'm not as familiar with the dynamics of Catholicism as I am with those of Christianity, but it is very counter intuitive to go about trying to get someone to understand, and even conform to your beliefs if you go about it in that sort of manner.
It seems immensely selfish of them to want you to be a Catholic simply because they want to keep up a sort of family image. If you are to be Catholic, Cristian, or whatever denomination suits you, you should want others to be apart of it because they actually believe in, and have faith in those beliefs.
I will be completely honest, I am a Christian, and I do believe in god, and I do believe it would be beneficial to be apart of the church. However, it is very understandable that you would be disinclined to do such a thing because of your negative predisposition towards the idea, partially, if not mostly due to your parents poor handling of the situation(s).
As for a immediate solution, I would suggest attempting to help your parents understand why you don't agree with what they believe in. If they still are unable to carry out a decent conversation with you, or able to provide a good reason for wanting you to go to church besides "it will make me look bad," then I'm afraid you may just have to play along enough to escape them, if it really is as bad as you have described.
While I do not agree with your beliefs, I also do not agree with the logic of your parents, and cannot support their reasoning either. If you are an "agnostic theist" simply due to the poor influence of your parents, then I would advise you try to look past this, and understand that disillusioned "religious" people are not what you go to church to be apart of, or become. It is to have faith in what is true and absolute. However, if you have other reasons for your religious affinity, then I suppose your reasons are a bit more complex.