Yes, Grealish has done worse, and for some unknown reason this particular fan cares.
The average prem league player gets paid 3 million pounds a year. If I got paid a small fraction of that I would avoid (and have managed) getting my name in the tabloids. It affects, or potentially can affect, Villa's financial statement, the line item called good will. I would be very surprised there is not a clause in player contracts that deals with such behaviour.
Having said that, there seems to be something self destructive about Barkley's behaviour. It would be interesting to have a sense of the underlying causes. I wish Barkley all the best in his future endeavours, and trust he stops digging a hole for himself.