Pete Carroll was an NFL head coach (twice) before becoming a college head coach.
harbaugh = bobby petrino, butch davis, steve spurier, lindy infante, pete carroll, lane kiffin, ...do i need to continue ?
Butch Davis was a successful defensive coordinator in the NFL before taking a college coaching job.
Lindy Infante was an offensive coordinator on a Super Bowl team before taking his NFL head coaching job.
Lane Kiffin wasn't a college head coach before taking the Raiders job. He was a position coach (the Raiders were just that desperate).
As far as college coaches coming to the NFL, there are also successful examples like John Robinson and Jimmy Johnson. Guys like Saban and Petrino soured a lot of the current NFL on the idea, but it's not like no college coach has ever made the successful transition. Throw in that Harbaugh was a fifteen year NFL player and spent two years on NFL coaching staff.
To answer the question, I would say no, you don't need to continue because the examples you've already given don't really prove anything. Most of them weren't even comparable.