When someone posts nothing but Catholic website postings and then doesnt expect their to be dis agreement then I think you have someone who will be disappointed a lot. If it is posted then it will continue to be disagreed with
I think this is the kind of thing where what is required is accuracy. Whether the teachings are from a particular denomination or church, or the topic of discussion is politics or science or anything else, it's one thing to disagree and argue coherently and another thing entirely to present misinformation as if it were true.
If someone posts Catholic teachings (and those teachings are known to be actual Catholic teachings) we can debate whether or not we believe they align with Scripture, contradict Scripture, add to Scripture, subtract from Scripture, twist Scripture, accurately interpret Scripture, or whatever else using citations. While we're doing that others with a different view can assess our comments and agree or disagree, also explaining why.
The problems come if people claim the Catholic church teaches something that it actually doesn't teach or revert to useless posts. I wouldn't see a problem with debating and disagreeing with any denomination's teachings but if someone starts posting comments like "why would you follow a church headed by the antichrist?", personal attacks against the Pope, or unfounded comments that either have no basis in fact or assume everybody in the group is like the worst members of the group, they are merely detracting from the discussion.
As with anything else I'd say disagreement is fine as long as you explain why you disagree, allow the other guy to explain why he agrees, and realise that on any given issue the other guy might be right.
I don't think it will shock anyone when I say I disagree with some Catholic teaching and also disagree with many other teachings. Personally I'd rather explore the areas of disagreement to figure out whether I'm right or wrong, whether my understanding of what any given church teaches is actually what they do teach, and why people who do agree with the teachings agree with them. Even if I don't change my opinion it's good to understand why others believe the way they do.