Excessive force on behalf of the bouncers, and idiocy on behalf of the drunks who initiated with aggressive posturing and continued to approach after it was obvious they were outmatched.
The first bouncer kicks his downed opponent in the groin after he falls. The second slaps him down again when he gets up and refuses to leave. A friend attempts to intervene and is punched.
No sucker punch here – a drunk challenges the bouncer to a fight, gives him plenty of notice and telegraphs a haymaker which fails terribly.
Security guards take down a man who has invaded the field at a soccer match. The guards hit him with their batons while restrained, and the crowd intervenes and attacks them in return.
The chief mistake by the guards was failing to appreciate how their actions may appear to bystanders.