In the post, the singer-songwriter said he'd initially asked Trump to cease use of the song, but then changed his mind after noticing that "Trump seems to genuinely like Y.M.C.A. and he's having a lot of fun with it."
It's possible that Trump's use of the song has benefited Willis personally as a recently adjudicated writer of the song in a U.S. district court case in 2015.
The musician went so far as to thank Trump for choosing to use the song.
In other words, he's about as principled as Trump.