Tyrann Mathieu's personal foul on the 2 pt conversion

Can anyone shed some light on why his hit on Baker was a personal foul?

I saw one step and Mathieu's shoulder to Baker's upper torso.

It feels like yet another BS personal foul call against the Saints.

It may have been a half second late, but I liked it. Didn't care about that call, but the BS facemasking call on Bresee earlier was stupid as was a PI call when the receiver ran into our guy.