At the time there was a lot of division about whether doma or DADT were good or bad, I'll give you that. It was contentious then, contentious in the decade after, and the one after that when it finally came to an end. The problem is that history tends to remember results more than motivations and it's clear that DADT and doma were bad for the lgbt community. DADT led to years of witch hunts against lgbt servicemen and women and doma was uses to violate the rights of the rest of the population for decades.
And therein lies the problem. If you believe there is never an excuse to violate a person's rights for any reason ever you will be opposed to doma and to DADT even with contextual information within your grasp. Legislation passed and enacted is easier to judge than off handed comments, because their impact is much more evident.
Is Sanders some diety incapable of error? Of course not. It is important to remember that in the 2000s the pro gay marriage stance was a problem states rights one. They were fighting against that very doma legislation, and against laws and amendments in many of the states. They were using the notion of states rights to create equality despite federal law not to create inequality despite federal law and that is an important distinction. The right side is always the one fighting ft equality.
Do I agree with Sanders stance on the marriage bill in Vermont? No I do not. I understand why he did it, it risked losing civil unions by opening the debate back up so 'soon.' I think that is a weak argument, but I know for a fact that Sanders did not make it because he opposed marriage at the time he made it in some failed attempt to be political.
Now of we look at the Clinton's doma and DADT well I'm not going to say I know better than everyone in the last 2 dwcades. The impact was obviously negative but there is some unknown chance it could have prevented a worse outcome. Under most circumstances I would interpret that as a failed attempt to be political, but I would regard it worse than the Sanders comments because harmful legislation was enacted that violated the rights of lgbt Americans for decades. I think we can agree that is worse? The other thing is im not sure that is all this was. Clinton is on record being fiercly anti marriage equality before during and after this time period. So no I don't think that she nor her husband were using this to help the gay community, I think they were acting on their conscience at the time which told them that people of the same sex could not be married or even form healthy relationships.
So yeah I have a very nuanced understanding on both sides. I'm disappointed in Sanders position and I reject his reasoning. But i am disgusted by Clinton's actions which resulted in decades of rights violations.