Of course disagreement by itself isn't being rude, but it depends on HOW you disagree. There are a lot of members here who have extremely valuable knowledge and experience to share. It's often very clear who they are, and their posts are well written. They are the reason I personally keep returning to the forum, as it should be. There are also those who carry the "holier than thou" attitude, and it's clear which members possess it, since they re-hash the same things in every single thread, and frequently personally attack other members. Sure we all have disagreements, but for some members it seems every single one of their posts is an attack on someone. I truly feel sorry for those people, as they must have a lot of insecurities in their life, and it takes away from other posters the valuable wealth of information this forum has to offer.
You can debate with someone without saying you wouldn't let them work on your bicycle or that their rationale is lacking. That adds zero substance to the thread, zero. You might as well go post on Facebook. There are a lot of older adults on here who act like 15 year old girls, and everyone knows who they are.