Is it fair to abstract this concept to make a general rule? You think people ought not impose beliefs on others which fundamentally contradict how those others see the world.
The problem here is that we can have mutually exclusive beliefs. Given your example, we can have:
Person A's belief: Any two consenting adults ought to be free to engage in a marriage that is recognized.
Person B's belief: Marriages can only exist between a man and a woman.
How do we resolve that tension?
Some things cannot be resolved, nor agreed upon. Everyone is free to engage in any sexual activity no matter what, though at times they might want to hide what they are doing from the legal authorities. In regard to adults, many sexual practices are optional, and none can prevent this from happening.
However, when some want the explicit approval of society of their actions, they turn to counterfeiting the definitions we have. This is nothing new, but it is a tool by those who cannot get approval from some so as to wrench power of approval of their actions no matter the cost.
Thus gay which used to mean a joyous type activity became hijacked to mean homosexuality, and now marriage has become an abomination.
Why, if these people want to have sex with same gender persons can they not just keep this defined as what it is? Because they are ashamed of their abominations, and now want to force everyone to approve of this by redefining what it is to be 'gay' and what it is to be 'married'.
Having accomplished the wrenching, the forcing of definitions - to be redefined, they now feel better because of having violated not only their partners but our entire society. Having thus brought all society down to their base levels, they feel lifted up, approved of, and go off trying to put down those who refuse to approve of this debasement. This is done by means of all powers they can bring to bear on this.
Just like I read here today, though being ignorant about it myself, the Pope now accuses the victims of wrongdoing. Yeah, way to go ! Put down those who think that refusing to be sullied and debased is to be opposed - that is how it is done now. The way of the devil for sure is how things work now. Step on the victims, step on those who refuse to join the debasement of our values. Soon those who refuse to join this debasement of our values will all be put in concentration camps, or something similar. At least, that is where things gradually are taking us.