Sin may be worthy of discussion. Even if one's personal view is completely potted, it may be entered into a discussion.
No one complained of a "christian discussion erupting". No questions were asked... only demands stated. (again.. based on composite reports by a range of ages).
The school room is appropriate but, at the same time, there is 'content' that parents would not endorse being taught in a school room because: the content itself is forbidden to be discussed there; or, the school room isn't the 'best' place. Of course, parents would want to know when teachers cross certain lines.
Appropriate for an outside group to barge into the room out of program? If I or one of the other "senior" skaters started preaching to kids, a discussion would in fact occur. In the school room, a teacher raising issues as a professional is far more actionable and discuss-able. Actions are weighed with accountability. An existing relationship creates context. Discussion and debate are learning tools. I see no problem with a "rogue" teacher bringing in new and even contentious information.
(Reminding me of the move in Ohio to turn biology classes into biology + religion classes.)
State mandated contention is another story.
From what has been reported to me through adults and skaters is that this group has made more than one trip to the skatepark but it was the most recent one where they actually entered the park with the preeminent message that skateboarding is a sin and that they were praying for people that were skaters. As far as I know, they were not addressing non-skaters. Their focus on the thursday visit was to confront skaters of all ages. In a previous visit, they wore all black, blasted some heavy metal music from speakers and held mock fighting and drinking skits. This was followed by "a minister guy" that came up to each one and "said a bunch of stuff" and then proceeded to remove the black clothing to reveal a pure white garb underneath. It was these white-clad teenagers and young adults that returned a day later to confront the skaters.
I'd really like to know what the skateboarders experienced and thought and how they navigated the situ.
Anyone who thinks skating is a sin is a kook to begin with. Like hearing a white supremacist. You just feel pity. Every kid I talked to can't wait to see them pop up again - pure entertainment.
One side note - years of street skating has put us in contact with some crazy street-types. Most kids I know can tell great story or two about how they were skating behind X building and were approached by Y asking/demanding that we Z. Insert your religious, political, civic duty, law abiding, criminal, homeless, rich-snob, security stooge and comments. Most skaters over 15 have been around long enough to hear how bad or stupid they are for trying to ride this thing. Having some people come to a public skateboard park just seems more novel than anything else. Totally harmless - but totally novel.
The under 12 crowd is another story. Approaching them is akin to child abuse. If they have an issue with kids that age taking up skating, they should direct their message to the parents. Make some flyers, hold a workshop. Show up on Helmet Safety Day at City Hall when you can catch 'em when they are really young. We'll make sure that our table is far far away from theirs - out of religious tolerance.
