I don't understand people that get upset and hostile at employees in these situations. When I go through self checkout I go in with expectations already set that it's very likely that at some point during the checkout process the machine is going to trigger an alarm and an employee will need to come over and override the alarm. It doesn't happen too often, but when it does my first reaction isn't to get all pissy and throw things at the cashier.
If you have no patience for this sort of thing, then go through the regular checkout. See if it takes longer going that route.