I wrote my post before hearing what the governor said but his points were basically the same that I wrote.
Maybe there's something in the Michigan water.
More seriously, maybe it has to do with Republicans in heavily unionized states like Michigan seeing that lots of union members are actually pretty decent guys. The big problem is the union leadership, not the rank-and-file.
Get rid of mandatory union membership and some unions will go back to helping their members. The rest won't be around for long, or won't have enough members to be a problem.