I wonder what do you mean by “moral relativism”? It simply means that
ALL the details of the act must be taken into consideration. The opposite is to arbitrarily disregard certain aspects of act… It could be “deontological” or some other kind of moral meta-system. But if the consequences are not taken into consideration, then the whole system is useless.
Of course catholics are also “relativists”. You should not kill, UNLESS you do it in self-defense or in the defense of others. You should not steal, UNLESS you do it in self-preservation or to keep someone else alive. You should not commit genocide, UNLESS God orders it. Strangely they have a general commandment against LYING, but they have no problem with a lie which would allow someone to avoid a death squad… but then they redefine “lie” (for example it is not a lie if the other party has no “right” to the truth, whatever that “right” might be). They also have no problem to lie to their children about Santa Claus or the Tooth Farie. Well, the commandment is not REALLY against lying, it is against “bearing false WITNESS”, which is against “perjury”, NOT lying. But such minor discrepancies are not relevant for the apologists.
So we have the not-so-peculiar event of a pot calling the kettle black. Amusing, isn’t it?
Now, let’s be honest. There are “intrinsically evil” acts, which cannot be excused. Expressing your love toward someone in a fashion, which prevents conception, is a horrible, inexcusable behavior. If your partner happens to be of the same sex, then there is no pardon to express it in a physical manner. Masturbation? Apage, Satanas! (Btw, I always found it funny that “apage” is just an anagram of “agape”. Could it be just a strange coincidence? There are a few…
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Oh, and for the nonsense of “if God does not exist, then all things are permitted”, just try a few illegal activities (like growing medical cannabis in certain states). God most certainly will not interfere, but the police might. So those activities are NOT permitted. It would be nice to see these meaningless one-lines disappear. (Fat chance of that.) It is also funny that these nonsensical quotes are always paraded by believers. Atheists seem to know how ridiculous they are.