I think part of the absurdity being pointed out is that "just standing there with your eyes closed and silently praying" is considered "harassment" at all. It just stretches the meaning of the word part the point where it seems meaningful.
Edit: I think this ultimately becomes a Sorites paradox. Obviously a whole mob of people gathered around an abortion clinic and silently praying while you're trying to enter is intimidating and should qualify as harassment, but one person doing that clearly is not. There is no point at which the number of people become "a mob" though.