Why? I don't think there will be that many true Christians walking with God when it happens. There will be a lot of false Christians, like those mentioned in the article, who will deny the Rapture because they weren't taken.
It’s possible to sin while saved, but it isn’t anywhere as easy as to sin before being saved. The Lord would generally be chastising them to show them the unprofitability of continuing to sin. Going into one of these “gay marriages” would be almost impossible, but that’s only IMHO.