Breaking out a couple of different areas I wanted to make comments.
The rulebook
For anyone wanting to look for themselves, the NFL rulebook can be found in a pin thread in the forum, or you can just
click here.
You want page 85, the section that starts on the left of "Hitting Passer's Knees 5)". Someone already posted the full text of it so I won't bother retyping it.
Was it forcible?
On the subject of was it "forcible", which it has to be for it to be penalty under that rule, if I'm called on to give my best interpretation I wouldn't call it forcible, no. If Brady hadn't mostly eluded it, then it might have have been forcible. But he did and he was little more than grazed. As far as I know the NFL doesn't throw flags for what could have happened that would have violated the rules, but didn't actually happen in reality.
Other applicable rule
Though in the referee's defense, I'll also point people to the top of the next page, 86, where it also states,
If in doubt about a roughness call or potentially dangerous tactic on the quarterback, the Referee should always call roughing the passer. So if the ref thought it was a borderline call on if it was a forcible hit or not, he's directed to throw the flag. I'm not sure watching the replay that I'd even say it's a borderline call. But if I'm watching it live and had to make the call on the spot, I might call it too, I can't really say without going through it.
I'm not sure if the "potentially dangerous tactic" gives the ref the leeway to throw a flag for anything he sees that is potentially dangerous, or only things that are potentially dangerous already covered by existing penalties. I'd have to hear Mike Pereira's take to know how it is interpreted, but that is potentially another area that might defend the ref making the call.
Ref didn't throw flag until Brady lobbied for it
I don't agree with this statement that I saw some others make. I think Brady comes up fist pumping because he believes it is a roughing the passer call, and not lobbying in this case. (Though I do agree he lobbies for calls a lot probably the most of any QB in the league, including when he doesn't have any merit for his arguing it... I just don't think that is the case on the Suggs play). I think the ref's hand is moving to the flag before he even really would have a chance to register anything from Brady even if Brady had tried. I don't see any justification for thinking that Brady's action on it caused the ref to think about it and then decide to make the call based on that. I think that is extremely clear cut that didn't happen.