I'm not a McBurnie fan and I've made no secret of that, but from what I've heard from people who were there (forest fans), this was absolutely not his fault.
Two injured players, one who's only 25 and one who's only 22, protecting themselves and each other against a baying mob of thugs.
Both nursing long term injuries as it is, they could have genuinely had their careers ended by those dickheads last night. Heartbreaking for the players and a potential financial nightmare for the club (see : JoC for an example).
Fair play to defend yourselves in that situation.
I'm aware it looks like the fan is on the floor, but I've been told that the fella apparently slipped over trying to fight Brewster and McB, so I'd argue that making sure he stays down is perfectly excusable in this instance.
It's what they teach kids at martial arts classes...if you put someone down, make sure they stay down before you turn your back