I accepted the quest from the Anarchists to kill Qui-Sai.

The problem is, I spoke to him earlier and now he is in the room filled with training warriors. I do not wish to fight an entire room after attacking him.

Is there a way to lure him out of that room into a corridor where it is quieter, and I could kill just him, not anyone else?

mmm if i remember you need to speek with someone about curing reekwind? or something before killing qui-sai or you can't do that quest.

Also if i remember, its been a while, attacking him will draw a group of guards, but i think after that initial fight is done you won't have trouble after, except for the person with the quest for reekwind.

I know it's a bit late (sorry), but whoever else also needs or wants to kill Qui-San:

You can kill Qui-San without anyone else becoming hostile if you close all the doors in the corridor outside the training rooms, use Morte's Litany of Curses to turn Qui-San hostile, and then have him chase Morte back to the rest of your party (see screenshot for the setup).

NPCs will only turn hostile if they see you either attack Qui-San while he isn't hostile yet, or killing him. Luring him away from other NPCs like this solves that problem.