At least we know they won’t have any guns on them. /sarcasm
Their preferred weapon is bombs.
They will also include some tall, heavy, and very strong young men as "security", and a few short, skinny, aggressive zealots to to dart in among and taunt the 2A supporters. There will be a number of pretty young women with cell phone cameras present to record the festivities.
Most of the counter-protesters will be unaware of these organizational details. They will be genuinely surprised if anything unpleasant actually happens.
The game is to publicly humiliate opposition, and to provoke an incident that can be used to motivate leftist supporters. It is a winning situation (for them) either way.