Everyone gets at least a little bit of nerves.
Try to remember that you’re surrounded by people who will render help if something happens, and any injuries sustained will heal in time.
There’s not really “good” advice to give, because everyone’s different. Take some time to find something that works for you whether that’s a pre-protest warmup, meditation before or after, breathing exercises, ideological or philosophical motivation, etc. Something is going to help you slow your heart rate and keep your head about you.
That is unironically evil.
They probably think it’s the funniest shit ever, but it’s just heartless behaviour. The kind of shit a cartoon villain would do.