Those laws aren't so much blasphemy as they are anti-discrimination. I'll admit to being largely ignorant of the american legal system, but from what I see on messageboards, there seems to be a strong emphasis on free speech trumping pretty much anything else. For comparison to the UK's free speech laws:
https://www.escapistmagazine.com/news/view/104844-Man-Goes-to-Jail-for-Being-an-Internet-Troll
Obviously, there are differences in that this man was just trolling, as opposed to the WBBC which was putting forwards a genuinely held belief. I definitely don't think that what the WBBC does is morally acceptable, but they do seem to be protected under constitutional law. English law, well, apparently not, and I know a lot of people can put forwards the slippery slope argument as to why free speech needs so much freedom. But I still don't see why we have to go down the slope. Whether you're talking about the UK or the USA, our civilisation should be sensible enough to plant its feet at one point on the slope and say "We're fine here. Not going up, not going down."