A US mixed martial arts fighter says allowing gay couples to become legally married is the first step on a path that could lead to people marrying animals, children or their siblings.

In a Facebook post, former Strikeforce lightweight champion Josh Thomson asked: “Should you be allowed to marry whoever you want? Before you answer that, should u be allowed to have more than 1 wife?”

The 34-year-old San Jose native then wrote: “Should siblings be allowed to marry siblings? My point is, where do you draw the line? I personally don’t care who you marry but I also am smart enough to know that it opens a gateway to men/women trying to marry young kids, siblings marrying each other and people having multiple husbands [and] wives. You have to think all of these things are okay otherwise your stopping them from being happy as well which is hypocrisy. Equality doesn’t stop with gay marriage, it just starts with it.”

He then added: “I’m not talking about just gay marriage. I’m talking about where does it stop? Where do you draw the line? People wanna marry animals, children, siblings, multiple husband/wives, etc?”