"Silencers" are considered taboo here because of the vagueness in the ATF laws regarding suppressors/silencers on other than gunpowder-fueled guns. From what I know of the federal laws, it isn't really illegal, but I am not a federal agent.
As for the sniper debate, I think it boils down to the fact that I don't see a chart for memorizing the forumlae of a bullet's projectile. I mean, let's face it, a SWAT/ERT sniper has an entire booklet that allows him to calculate the effect of the wind on the bullet, the humidity, etc. I don't see that in paintball. By what you guys describe it might as well be an LRRP standing there. They aren't snipers, just really good shots. There has to be a defining line somewhere, and I think it is at the science and training of it all. I think a sniper should automatically have a B.S. in Applied Science attached to his name, but that is just me.