I think it doesn't take much to realise the bill isn't about piracy really, but about establishing/expanding corporate control over the Internet. People like Rupert Murdoch, companies like Disney and organisations like ASCAP (who want to make Creative Commons illegal!) want to control and censor what people can say/do on the Internet (especially about them), never mind the guff about piracy, and are using their paid-for congress and senate (via PIPA) to attempt to do so. As has been pointed out, this isn't so much unconstitutional as anticonstitutional.