One could argue gay people were not denied the right to marriage, they just couldn't marry who they wanted. Polygamy people aren't denied the right to marriage, they just cannot marry who they want [in terms of quantity and person]. The Polygamy person does not receive the benefits to all their "wives" and it's only for one single person. In each case in the past, a choice had to be made. That is how they are very similar.There is no pressing issue. There is a YUUUGE difference between gay marriage and polygamy. People practicing polygamy can still go and get married to at least one person (since I've now learned it's not legal in any way) and make use of the benefits involved with state-recognized marriage. Gay people were literally denied the right to marriage AT ALL.
Now if some group of people were denied the right to marriage AT ALL just because they had an interest in having multiple partners, that'd probably be a bigger issue.
I honestly don't see how someone could be for gay marriage but against polygamy choice in marriage. They are one in the same for the thought logic. I think the government should allow both. However, as I stated earlier I don't see it happening as polygamy doesn't have the money behind it to go through our government.