I also don't understand why things like homosexuality are orders of magnitude more important than all the other sins named in the Bible -- and often far more clearly and unambiguously.

You don't see Christians protesting outside credit card companies because they engage in usury, or against companies that make their employees work on Sundays, or for policies to help the poor, or anything else like that.

Ultimately what it comes down to is that ideology/religion is the cart, not the horse. People have prejudices and preconceived notions, then they cherry pick from their ideology of choice to rationalize them. People think gays are icky and weird, so they cherry pick from the Bible to support discrimination against them. But usury is profitable so they ignore those parts.