Saying that a denomination is ‘bad,’ in the context of this thread, simply means that their attitude towards Catholicism is negative. It doesn’t mean the denomination is bad in and of itself. You are free to disagree about whether or not a denomination is anti-Catholic, but calling it that is not an insult. It’s just the observation of a trend! And, as noted on this thread previously, there are MANY individual exceptions.
Also, it is not a sin to call a “Christian” church non-Christian. This is an objective statement that can be made based on a survey of a denomination’s beliefs. For example, if a church calls itself Christian but decides to believe that Jesus is not God, we could objectively say that they are not Christian, even though they consider themselves to be, because they don’t fit the definition Christian. This doesn’t mean that they aren’t sincere in their beliefs or that they will go to hell.
Finally, keep in mind that the anti-Catholic attitudes tend to be expressed OUTSIDE of church services. I don’t know of any pastor who would use his sermon to bash a particular religion. So it’s possible to attend an anti-Catholic church without noticing any bias. The bias tends to be among the people, outside of church, manifested in their attitudes and comments. For example, a Methodist friend of mine has made anti-Catholic statements directly to me, though I’m sure she never heard them during the Methodist worship services she attends!