This is almost surely an example of euphemism in the service of politeness. My favorite example of Paul Graham wording in the service of saying something firm nicely is "When disagreeing, please reply to the argument instead of calling names. E.g. 'That is an idiotic thing to say; 1 + 1 is 2, not 3' can be shortened to '1 + 1 is 2, not 3.'" I love the use of "can be shortened to" there, as if pg's only concern is saving people extra keystrokes. I think the polite phrase "stealing users" here similarly leaves another idea unexpressed.