Thing is, I wouldn't see it as threatening. If Flamingo or 445driver backed down meekly every time a s**thead started mouthing off then it would just encourage worse the next time. The kind of thing that they say doesn't escalate the situation (since it doesn't take 'power' or 'respect' away from the scrote) and at the same time lets them know who's really in control.
It's similar to how police deal with arresting people in rough neighbourhoods - they're firm enough with the bystanders to let everyone know who is in control, but not so much so that they (the bystanders) turn into a mob.
If you ever watch nightcops and similar programmes you'll see how the police deal with aggressive individuals and it certainly isn't by inflaming the situation.