Yes, cut them off.

The ones that are bolting don't make good bulbs unfortunately, I would eat them as scallions.

Concur: Red Bull is a long day storage onion. Starting them in the fall gets them large enough to seed the cold winter causes them to go dormant and when they awake in the spring they are programmed to bolt to seed. Sow them 6-8 weeks before transplanting into the garden. They won't begin to bulb before June.

Okay, that makes sense.