https://www.youtube.com/watch?v=eL-AE1ZRp0k
If you think Porter was out there to instigate, I would urge people to watch this video from around 9:50 to around 10:11
It starts with Joey Porter at the bottom of the screen, walking across the field next to the Steelers trainer.
You see Burfict cut him off to pat Brown on the shoulder and a Steelers trainer pushing his hand away, which cuts Porter off from the group.
Then and ONLY then is he surrounded by Bengals. He didn't seek out the attention.
As Porter continues on, you can be SURE there's some talking going both ways. He even turns around walking backwards, with both sides talking.
And then at 10:11 or so, Gilberry comes in from behind and bumps Porter.
The ref tries to separate everyone, and Pac Man does his thing.
People have this misconception that he went out there to find Bengals players. The tape proves otherwise. He very well may deserve a fine for opening his mouth at all, but intentional or not, he baited the Bengals into doing something stupid.
And it doesn't matter if you think he should've been out there. He had permission from the refs to be there. Given that Pereira said 13 different coaches were on the field at that moment and the Bengals weren't penalized earlier in the game when the freaked out on Bernard's hit, the refs treated the situation exactly as expected, including Pac Man's reaction.