Yelling at incompetent or lazy co-workers isn't your responsibility, it's your manager's. Escalate the issue and let them be the asshole. And if they don't handle it, well it's time to look for a new job.

>> Yelling at incompetent or lazy co-workers isn't your responsibility, it's your manager's

First: Somebody hired these people, so are they really "lazy and incompetent"?

Second: There is no one who's "job" is to yell at incompetent or lazy workers.