Kk thought you were just trying to be a dick. I'll happily answer that though so here goes:
Hmm okay, well first off you're right it wouldn't ruin my life in a literal sense, however I'm a proud guy and such incredible public humiliation paired with the fact that it was posted online would probably mean I wouldn't forget that event anytime soon.
If that happened to me the same way (it wouldn't because I'm not fat) it would undoubtedly by the most humiliating moment of my life so far, and possibly ever. I can't even imagine the shame in the after math, trying to head to a bathroom covered in pie and cake, then having to shamefully go back to retrieve my purse and shoes. It wouldn't ruin my life, but it would be a really shitty and horrible experience that I wouldn't forget anytime soon.
As for the beating up thing, I can honestly (yes lol honestly) say I would seriously hurt someone who threw a pie in my face.
I posted this on /r/progresspics over 5 months ago when I was muscular and 175lbs. Now I am far bigger and closer to 190lbs.
The most embarrassing part of this scene is the fact that she never got the clown. The clown just kept laughing at her, he "won" in a sense.
Again, I'm a proud guy. I highly value my humility. Look at those pictures, there's no chance in hell I'd let anyone get away with that. I would hop over the escalator railing (I'm 6'3 so it would be an easy hop) onto the down escalator, and I'd absolutely 100% start doing whatever I could to hurt that guy.
Not because it's the right thing to do, but because I know myself well and I know that if someone did that to me, I'd be really really pissed.
So, in conclusion no it wouldn't literally ruin my life, but it would be a horrible experience I wouldn't soon forget. Finally yes, I would "honestly" beat the shit out if that guy (fine now literal shit but it's an expression).