Correct, no right to bear arms people think it stops bad guys shooting people, only that it caps the deaths - i.e. you'll have a few killed then the bad guy is dropped, rather than they get to go killing dozens of people at leisure without resistance until the cops arrive (and presumably, wait outside while the bad guy continues killing, to "secure the perimeter" or whatever).

The theory then is that this will act as a deterrent - an angry bad guy wants to go out taking dozens of people with him - a few people wouldn't be "enough" for his grandiose end.