Gossip consists of two people bonding with each other at someone else's expense. Over drinks after work, new friends speak ill of a co-worker. They do not mean to be mean. Rather, their unkind words are an offering of kindness to each other, as if to say, See how much more I like you than I do him.
We appreciate similarity by contrast with difference. Amid the foreign speech and customs of other cultures, we make instant friends with a fellow countryman, chattering like long-lost companions, though on streets at home we would pass each other by as strangers. We exchange phone numbers but never call, because once home among friends, a shared homeland is an unremarkable bond.
A common enemy makes former enemies friends. Political parties battle each other in times of peace, while national unity is rarely so strong as in time of war. Widening the logic, if a hostile race of extraterrestrials arrived to annihilate earth, Iran and Israel would hold hands for the good of humanity.