Whilst I do not support abuse, racism or Twitter "pile ons", I fail to see why, what Marcus has done for charity precludes him from criticism in his (highly paid) day job.
If I were to raise thousands of pounds for charity, but when I went to work lost the company a contract through my incompetence, I would expect to be criticised for it. No mater if my performance in the company to date had been exemplary. The two things are not related in any way. You can't be above criticism just because in a different area of life you do good works.
Jack's tweets and retweets trying (and failing) to support the message #bekind to Marcus does not address that on the night he was unsuccessful at his job. I do not understand why you can't praise him for his charity work, but critique his performance and still feel sympathy for him. These things are not mutually exclusive.
Again I say I do not support abuse, but we have always assessed and made judgements about a team's (and individuals) on pitch performance. Indeed we pay sports presenters on TV and radio huge salaries for doing just that. It can be done in a non abusive way. If they can only say #nicethings about the players performance, then what is the point?
The way Jack jumped to defend Marcus, whilst ensuring that everyone was aware that their paths once briefly crossed, was cringeworthy.