One odious habit of far leftists and other sick bastards is that they insist that things which are either blatantly false or else controversial be included as stipulated fact before agreeing to proceed with any further discussion.
It's generally more subtle than that. The more common approach is to present something as "a problem," about which some action is required. And in many cases, what is presented as "a problem" really is a problem. It's more a matter of whether the problem should be addressed at all and, if so, how it should be addressed. Those on the left usually have the advantage in such cases because 1) they're prepared beforehand and we're not; and 2) they go to all the meetings beforehand, and they have input to the agenda for
this meeting, which is why this topic is on the agenda to begin with.
Another common ploy is to play on sympathy as a means of distracting from important points. The "same-sex marriage" thing is a case in point. The appeal to sympathy went, "Isn't it terrible that people who love each other are denied a formal acknowledgement of their love and commitment?" Speaking for myself, I have no problem (other than finding it rather sad) with people loving and being committed to a member of the same sex, and the sympathy ploy has a certain credibility. I actually don't mind acknowledging a union as, for the people involved, it's probably better than the alternative. The problem is that it's not "marriage" in the same way that men and women can get married.... and have children and raise children and continue the species. The dynamic of that kind of marriage is drastically different from the kind of union that a same-sex couple can have. The appeal to sympathy is in large part a means of disguising the fact that we're being asked to affirm the pretense that they
are the same. If we limit the definition of marriage to those areas where the differences are negligible, then not only do we eliminate those areas where the differences are crucial, we also fail to enforce the very things (related to family) that make marriage so important to society.
The defense against the sympathy ploy is mainly to name what's really at stake, in a way that does not strengthen the sympathy ploy.