Here's a strategic reason to support Amash, in addition to all the other reasons, which are plenty enough as it is.
The Michigan GOP primary awards most of its RNC delegates on a per congressional district basis. I believe the winner of each congressional district gets three delegates regardless of the statewide vote.
The RP campaign could focus campaign resources on just a few of Michigan's congressional districts and have a chance of winning delegates even while losing the state. And if Amash is in Congress and endorses RP for president, then, with his influence in that district and his network of supporters in place and fresh off a 2010 victory, his district would be in play for RP.