Save for a few bad eggs, Bill Belichick seems to be cordial with all of his former assistants who move on to greener pastures. If you watched the excellent "Belichick & Saban: The Art of Coaching" documentary on HBO, you'd know that Belichick is happy to send his guys off to bigger and better things, so long as they don't, as he says, "try to tear down our program." In other words, as long as they don't try to poach guys from Belichick's staff to come with them to their new organization.
Judging by a video clip currently making the rounds on social media, Matt Patricia, current head coach of the Detroit Lions, has done nothing to irk Belichick since leaving New England. That explains why Patricia, Belichick and New England offensive coordinator Josh McDaniels were seen yukking it up at the Senior Bowl, where the former Patriots defensive coordinator is coaching one of the all-star teams.
In the clip, Patricia can be heard immediately imploring Belichick and McDaniels to not say anything, because he's mic'd up, which is not suspicious at all:
Given the Patriots history, this might seem suspicious, but I can assure you it's not. Please carry on.
All jokes aside, there really is nothing to see here. I'm not trying to be snarky. Patricia was just notifying them so they didn't curse or say anything disparaging about his 9-22-1 head coaching record. It's like when you call someone and they put you on speaker around other people and they say "hey, you're on speaker phone" so you don't say anything dumb. Common courtesy from Patricia here.