How do I exclude a list of values using a filter in Google Sheets?

In Google Sheets, I have a filter that does this:

=FILTER(A:K, B:B <> "username1")

That works to exclude all rows that have username1 in the B cell. But I want to exclude a list of usernames. So I tried:

=FILTER(A:K, (B:B <> "username1")+(B:B <> "unsername2"))

But that excluded nothing. I would have thought that filter should exclude all rows with either of those usernames.