Bill Walsh - First of all started as a college coach, had first HC job in college, and did great at Stanford, before jumping to NFL. There he, well if you don't know what he did there, no point telling you. Then after getting burned out during a long and successful stay in the NFL, he took 4-5 years off and then returned to revive a dismal Stanford and had 1 great year and 2 bad years before retiring from coaching. This had to do with his age and being burned out, not NFL vs college experience and he still had 3 good seasons vs 2 bad seasons (the opposite pattern of our current coach, who you defend) and is remembered as one of Stanford's more successful coaches...oh, and he was 3-0 in bowl games. Man what a terrible, terrible example this is.
Bill Callahan - He took over a loaded team from Gruden and maintained it for one year before turning it into a complete dumpster fire and being fired the following year. Just a poor NFL HC hire, who still did better in college than he did in NFL. 27-22 in college vs 15-17 in NFL. Weak, next.
Mike Sherman - He started as a college coach, but did get his first HC job in NFL and promptly flunked his way all the way out going from NFL HC, to NFL assist HC, to NFL coordinator, to college HC, to high school HC (in that order). This is the closest thing you have to a good example and the guy is a total anomaly starting at the very top and flunking his way all the way down to the lowest level. This has little to do with NFL Vs college experience and more to do with him just being a poor HC. Close, but still fairly weak example.
Chan Gailey - This one is just laughable at best. He had TWO (2) COLLEGE Head Coaching stops and one arena league HC stop before his first NFL HC job in which he lasted 2 years before being fired. (((AND))) he was significantly better in college than in the NFL. 68-43 in college Vs 34-46 in NFL. Complete joke of an example!
Al Groh - This guy coached in college from '68 to '86 AND had his first HC stop in college before moving to NFL as an assistant, where he ended up having ONE season as a HC before being let go and moving back to college. Weak, just plain weak and inaccurate example..
Lane 'F'ing' Kiffin - Are you kidding me? He lasted 1 season and 4 games in his only NFL HC stop, going 4-12 and 1-3 respectively. He then went to college where he didn't meet high expectations, but did way, WAY better than he did in NFL. 35-21 in college Vs 5-15 in NFL. Really reaching here..
Forrest Gregg - This one is absolutely hilarious!! Resorting to using the guy who went to SMU directly after it received the "death penalty" from the NCAA for his only 2 college HC seasons. Yeah, your list of examples must truly be never ending if this is the level you are going to.
You continue to display that you lack the requisite football IQ to discuss basic football matters.