It's easier for him to express his feelings physically than via words. How could he possibly put everything he feels for Tailgate into mere words? It's too important to simply be said.

He smiles as Tailgate presses his cheek against his hand and brushes his knuckles against his faceplate. He doesn't deserve the devotion he sees in Tailgate's gaze, but it makes him impossibly glad to see him happy. He would tear the stars from the heavens to keep this one safe.

He'd do anything except tell him that, apparently.