The best part of this has to be the American soccer fans twisting themselves in knots to rip Messi, only because they hate MLS.
Thankfully I haven't seen any of that. And it would be truly weird, if you think about it. MLS haters generally fall into two (non mutually exclusive) buckets:
1) I want USMNT players to play at the highest levels in the world, which probably means Europe and particularly means Big 5.
2) I personally have become a fan of Big 5 (usually EPL) football, and so I'm just not an MLS fan and/or feel the need to look down on it.
Group 1 should be stoked that the quality level of MLS has improved enough, and the business fundamentals enough, to pull in a guy like Messi who 6 months ago was a linchpin of the world champions. Better MLS = better US talent development and competitive environment for USMNT prospects.
Group 2, unless they were Barca or PSG fans, should be happy too, because even if you think the quality of play in MLS is too poor for you to deign to watch, Messi coming means it's getting better, and soon you may have football worth watching that you can actually attend in person.
Other than Barca fans, I haven't seen anyone upset about the deal. Have you? Or are.you just assuming MLS haters are going to hate under all circumstances?