Brady should have congratulated to Garappolo on his first NFL TD, but who am i to say what Brady should do. Brady does not need to prove anyone wrong, he was a 6th round draft pick and arguably the best QB in history, definitely in the top 5 of all time. Brady knows what he is doing.
With the fact of the matter being that Tom Brady did a lousy job and was benched for it, he acted very childish in not congratulating Jimmy Garoppolo. There may come a time when these grown men start acting their age and not like spoiled children. Garoppolo did an amazing job and therefore at very least deserved a handshake and congratulations for his efforts.
While few people alive can perform like Tom Brady on the field, it doesn't give reason that Brady should not show some support to his understudy. Jimmy Garoppolo may aim to replace Brady one day or even to move to another team in need, but his actions were simply in support of his team. Actions that should have been recognized by a man seen as the leader of the players, the starting quarterback.
Tom Brady is clearly on the last act of his illustrious career as quarterback of the New England Patriots. The Patriots, for the second year in a row, spent a high draft pick on a new quarterback. The Patriots were destroyed by the Chiefs, so they gave Jimmy Garoppolo some valuable experience. Tom Brady should congratulate the rookie and teach him what he knows.
I don't see any reason to demand that someone congratulate someone else for a touch down. Let's be honest people are people. No one should feel required to congratulate someone just because some one else says they should. Tom Brady is/was an excellent player but that doesn't mean he owes Jimmy Garoppolo anything.