Rethinking "Immoral" Acts

In his book Logic and Sexual Morality, John Wilson brings up the following:

Yet there is at least one other distinction which is much more important: the distinction between those who believe in what I shall call the fallacy of discrimination and those who do not. The fallacy runs as follows:

(a) x is an activity which can be of great value or significance for human beings;
(b) therefore people ought to use discrimination when they do x;
(c) therefore we must teach them that they should only do x in forms restricted by rules, precepts, principles, or ideals, because otherwise x will become devalued, meaningless, irresponsible, or positively wicked.

The argument in which I have outlined the fallacy contains (at least) one illegitimate move, and one key ambiguity. The illegitimate move is easily seen and dismissed. It does not follow from (b) people ought to use discrimination that (c) we must teach people anything specific. For it is not clear that we know what to teach in all cases, and if anything is a case where we do not know, it is surely sex.

Certainly, some types of behavior might be more valuable than others, but that doesn't mean other kinds of behavior should be -prohibited- or even -discouraged-.

I see eating dinner as valuable when I spend it with all of my friends, cooking it, and cleaning it up afterwards, but I certainly cannot do that every night, otherwise I wouldn't have time to do other things like homework! Are my other dinners less valuable or less meaningful? Sure! But should I say that eating a sandwich by my lonesome is immoral? I should hope not.