De-Emphasizing marriage and abolishing State Marriage would definitely have been seen as liberal, up until very recently. Certainly, removing state control over an area where it is not required is definitely liberal. That was the understanding when I began to back this long term goal back in 2004.
That is, up until recently. Now that marriage equality (a cause I support myself) is the primary progressive movement in the West, it seems that many liberals don't think of my position as liberal anymore. Why? Because it would render marriage equality 'useless'.
Certainly not. In fact, the reason why we are fighting for marriage equality is because we have to work with the present governmental system for a while yet. Marriage equality is currently easier to achieve than getting government out of the business, but the latter should be our long term goal. As for de-emphasizing marriage in culture, that is the only way to achieve freedom and equality for all (globally) in the long run that I can see. Therefore, the two goals do not contradict each other - one is short term and the other is long term.
Another thing is that 'marriage' is a Western export, and one that has been assimilating other cultures in a bad way. Certainly, the end of marriage-as-we-know-it will allow these cultures to return to their roots regarding how relationships are formed and socially recognised, and give relationship multiculturalism a go.
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