'I see nothing Christian about the activity that this guys planning to engage in.'
Realy? If exposure dosen't shame them, they won't care; and if it does......they shouldn't be there.
Sorry, but that argument does not wash. Harrassment is harrassment, and its immorral and sinful behavior.
Taking it upon yourself to expose the sins of others to the world, is not your place... What was it that Jesus said about that?? Something I recall about those without sin casting the first stone?
I am absolutely amazed that so many supposedly "Christian" people wholesale ignore the actual words of Christ and his father when attempting to justify their hypocrisy.
The bible is quite clear about how a believer should deal with a sinner... and what their moral obligations are. And nowhere does it say you shall intimidate and harrass and coerce them from their path. Inform them of their sin, or suffer responsibility for them... but it does not say it is your job to drive them from their path.
Islam takes that belief system... obey the edicts or die or be punished in this world.... Christ did not advocate that sort of thing at all.