He was a Republican long after Republicans were no longer conservatives.
He's just not down anymore with the back corporate interests at all costs, anti-science, kowtow to the Christian religious right, vilify anybody that doesn't agree with you, thinly disguised bigots that have hijacked the Republican party.
Scarborough just took a lot longer then most of the actual conservatives to realize that the Republican party left them.  As far as who cares?  Conservatives do.