I disagree. Treating a group of people as second class citizens is unjust, and hiding behind the bible doesn't make it acceptable.
And no where in the bible does it say " thou shall not trade with a gay person". They argue that they now follow the New Testament, but cling to the line in Leviticus of the Old Testament that says god don't like gay people, therefore, they rationalize, they shouldn't serve a gay person because god doesn't like gays in the old testament though it doesn't actually tell them that they can't trade with gays. I mean, Jesus accepted all sorts of sinners into his flock, right?
That's cherry picking -- Their convictions are bigotry, and that doesn't fly with me.
There are tons of examples of slavery being acceptable in the Bible, but I dont see "convictions" by religous bigots to acquire slaves.
Of course, it's against to the law to have slaves, (because it's wrong) just as it should be against the law to discriminate based on sex orientation (because it, too, is wrong).