[mcguire]

'Avant-garde', as a military term, is obsolete in English; the English word is now 'vanguard'.

'Skirmish line', to my knowledge, has no accepted non-military uses, but even if it did the interviewee is clearly referring to the military formation and therefore considering the protesters to be hostile enemies.

[CompanionCuuube]

Well, they are throwing unspecified bottles of liquid at them, so they're not peaceful protesters either.

[Doxin]

There's a clear difference between protestors and enemies no matter the amount of hostility. Thinking of the protestors as enemies is bound to escalate conflict instead of deescalating it.