For me, at least, is how they don't want to know you if you don't line up with them. Facebook is an eye opener, where people's lives are laid bear and umbrage freely taken that one might have differing views. And heaven forbid you might actually discuss something where you disagree.
There are exceptions. I really Appreciate Grahame Baker, with whom I've cycled occasionally. He has diametrically opposed views to mine on a whole bunch of core stuff, yet we're still friends.
Certainly it's much easier to get along with people if you're not watching your back continuously, but if that's the case, is it really friendship anyway? I've expressed before on here a desire to really speak what I think, but either I really am a much freer thinker than many (seems unlikely) or I lack the social conscience that requires certain things that may be considered unthinkable to be thought but not said.
For example, I've found it funny how people do religious stuff 'out of respect and reverence' for God. I pray sometimes when I'm sitting on the loo (bet some of you do too) because God doesn't have to wait quietly outside the room until I'm done & he's not fussed about the biological stuff that we hide. Ever thought that He's there with you while you're making love to your wife/husband/girlfriend/boyfriend? Or while you're washing up? Or fixing the car, covered in grease and oil? Or muddy and stained after working in the garden? Could you talk to Him at such moments? So who are we dressing up for on a Sunday again?
Maybe I understand why people don't like what I think sometimes after all.