First, they weren't former close friends who started an actual *civil war* and needed time to lick their wounds. Second, neither side killed someone the other was close to.
Bucky and Sam both understand what frame of mind Walker was in during that fight. Their goal was solely to take the shield back. Walker was on edge, but they knew that going into the fight.
During the finale, there wasn't really a point where they needed to rely on trusting Walker to have their backs. And though it seemed like Bucky was bantering with Walker, I saw it as him being his usual snarky self when he's feeli