They inject their politics into everything because pretending they are morally superior for holding XYZ stance on <given issue> is the only thing that gives them a sense of self-worth. Liberals are typically inadequate in nearly every facet of life, and aligning themselves with a GroupThink that tells them they're better than everyone outside the group is their only chance to feel like something other than worthless. That's why they ceaselessly vomit their politics in every direction.