Now it's time for the rest of the story...
If Amulek was a polyganist and took these wives, he did so while in rebellion to his calling and before he met Alma.
What happens to Amulek in the end?
When he gets righteous and obedient to the Lord his entire family rejects and abandons him and he is forced to move in with Alma.
So if this topic was an attempt to justify the practice because of slight chance that Amulek practiced it at some time..... Uber Fail.