On the contrary, from my experience it isn't.
Sorry, I could not resist the opportunity. But seriously, I don't often see people disagreeing for the sake of disagreeing. More often, they'll point out different aspects, or their own perspective on a topic. To be honest, support and affirmation are perhaps a bit rarer than they should be, but I've rarely perceived disagreement to be hostile, as opposed to misunderstanding, or legitimate and resolvable via further discussion.
More datapoints, anyone?
If other people disagree with what I write they usually do it for the sake of disagreeing. However if I disagree... ;)
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.