Ask them to explain what moral standard they are appealing to when making these statements. Since I believe they are appealing to the standard of “tolerence,” ask them if they think (not feel) it’s right for a gun business owner to discriminate against a racist, who might use such weapons against the object of their hatred. Ask them if they think it’s discriminatory to ban a convicted pedophile from schools?
The point of this exercise is not to declare these practices as moral, to declare them immoral, or even to say they are comparable. The point is to show that tolerence in itself is not enough to show whether an action should be discriminated against or not, because otherwise all actions must be tolerated, including murder and rape. A higher level of moral standard must apply.
Modern thought, however, does not have such a standard, for it’s moral standard is based not in Divine Command, nor in natural law, but rather in the power of the State, meaning that those with power determine what is righteous. Morality is based on the whims of the age’s fads. Why do you think these people work so hard to legalize these things? It’s because it is not morally correct, it is not safe, until it is written in positive law. Therefore, they work to have the State legalize gay “marriage” or define a human being as a post-womb child, and so forth.
They are the neo-fascists: if the State (notice how moderns capitalize “state” like Christians capitalize God?) can define what marriage and what a human is, then why can’t it define a human being as, say, a non-Jew? What if, in the next age, the State defines a human being as a non-homosexual?
However, just as Chesterton wrote in
The Man who was Thursday, their are two kinds of “anarchists” (he means intellectual anarchists; those who rebel against tradition and the like), those who are innocent, the manipulated, those who do not know what the ideas actual point to, and those who are guilty, the high priesthood, who really do know what the logical end of their ideas are, and find joy in it
To really learn the errors of ideas, one must look at their logical beginnings (axioms,
a priori assumptions, etc. Modern Biblical Scholarship has a tendency to assume miracles are impossible
a priori, and thus begs the question against the Christian, as well as being anti-science), and their logical ends (most people don’t take their beliefs to their logical conclusion. Materialism ends with nihilism, yet Gnu Atheists talk about how great the world is without religion

I have respect for Nieztche because he walks to the end of his logical cliff (and over it, sadly). Moderns (English flatheads

)avoid the logical ends of their nihilistic worldview by indulging in food, sex, American Idol, and other distractions).
To convince others of your side, however, not only do you need to examine their ideas coldly, but also examine the persons’ heart warmly. As Bishop Fulton Sheen was fond of saying, do not just look at what a person says, but why they say it. Some people just won’t be convinced, as they are stubbornly in sin. Jesus says to wipe the dirt off your feet and move one (pray for them, because Christ also talks about how he will punish them worse than Sodom

).
Christi pax,
Lucretius