What Mara is upset about, of course, is Beckham's touchdown celebration during which he mimed the act of a dog urinating on a fire hydrant.
I think we can all agree that this was a pretty silly way to celebrate a touchdown, and one that was guaranteed to draw a penalty that cost the Giants 15 yards. I think we can also agree that Beckham has a bit of a history of similarly silly acts that have cost the Giants penalty yardage, cost Beckham money in the form of fines, and generally "looked bad," as PR folks would say.
But if the Giants are going to handle this internally, why is John Mara emailing Mike Vaccaro about it? And why are the Giants so insistent on repeatedly criticizing their best player through the media? (Especially when doing so has clearly not gotten the desired results?) At what point does the Giants' handling of Beckham come under the same type of scrutiny that they are happy to apply to Beckham himself?
Beckham is almost literally the only player on the Giants capable of producing any offense. That's not to say he should just get to do whatever he wants with impunity, but maybe they should try to find a way to positively affect his behavior that doesn't involve public castigation every time he does something the franchise views as wrong. It's probably not a good idea to poison the relationship, because eventually he might want to leave, and if he does, the Giants could be left with not much else.