I bet you didn't know the FARC has taken on a stance on gay marriage. Their take is that it is an understandable demand, but not revolutionary. The true revolutionary destroys marriage entirely.
As I read I wondered how it was relevant to the peace talks (the website is focused on those talks) and here is the answer.
Promoting an egalitarian transformation of the social structures and changing educational structures, designed to meet emerging community needs, is to rethink the concept family", without linking it to marriage. The marriage contract would then become unnecessary.
For a group supposedly seeking to integrate itself into Colombian society, this doesn't seem a very fruitful argument. "Support the peace talks and together we can make marriage unnecessary because we're all family" doesn't have a good ring to it.