Christians: What's bad about wool and linen blended together?

[BluffTHIS!]

It's a matter of doctrine based on biblical interpretation and you can do a search on an online bible to find where the NT expressly includes the decalogue, makes it clear various non-ethical laws don't apply to Christians (Acts), and even goes so far in the words of Jesus as saying the spirit of the law is summed up in loving the Lord with your whole heart, mind and soul, and in loving your neighbor as yourself. No major christian denomination holds otherwise.