Personally I don't think this is a big deal. As it says in the Bible, "judge ye, lest be judged" and "let he who is without sin cast the first stone". Since I'm pretty sure every single one of us has given someone the finger, I can't see how Mr. Met deserves to get suspended or lose his job over such a ubiquitous gesture.
Last night someone shared video of Mr. Met flipping him off during the Mets 7-1 loss to the Milwaukee Brewers. He claims that asked for a high-five and that was the response.
I call shenanigans. Mr. Met is a professional, unlike that abomination The Philly Phanatic. He wouldn't just lose his cool over someone asking for a selfie or a high five. And since the video starts with the middle fingering, there's no way to know what transpired beforehand.
More importantly, Mr. Met only has 4 fingers. You can't have a middle finger if you don't have an odd number of fingers. Where's the middle?? IF THE GLOVE DOESN'T FIT, YOU MUST ACQUIT!!!!
The Mets are playing it safe and have issued this statement: