My headcanon is Matt has a kneejerk distrust and dislike of anyone who doesn't like Foggy. Because to him Foggy is sunshine and rainbows, so what's not to like?
On the other hand, Foggy rarely cares if anyone dislikes him. He shrugs it off easily because he doesn't need the approval of anyone besides his loved ones. But he finds it really funny (and secretly sweet) when Matt gets mad about people not liking him.
Gen or Matt/Foggy, somebody doesn't like Foggy, Matt literally can't understand
On the other hand, Foggy rarely cares if anyone dislikes him. He shrugs it off easily because he doesn't need the approval of anyone besides his loved ones. But he finds it really funny (and secretly sweet) when Matt gets mad about people not liking him.