Just as you would get differences of opinion, criticism, rude comments, etc. in any city on the planet with over 100,000 people, the internet isn't any different. Internet interaction may even cause an increase in the mentioned behaviors, regardless of common ground and interests. I second NadMat's thoughts/comments.
The number of good replies and responses on this board far outnumber the rude, flames, and the crass. I find many humorous, in their absurdity. If there is anything I don't care for, I just bail out.
DandyDon almost always mentions the search function to new members. It's a nice way to find out if anyone has asked a particular question or started a topic before. Checking that may gain the info you desire or will at least let you know you are treading into murky waters by reading first. Shouldn't have to do this, but; like before, 100,000 people - it will occur.
Hope you enjoy the board and stick around.