Getting away with it in private won’t cut it.
1 Now, just as man’s mind may be raised up to God by means of corporeal and sensible things, if one use them in a proper way to revere God, so, too, the improper use of them either completely distracts the mind from God, and so the end of the will is fixed in inferior things, or such abuse slows down the inclination of the mind toward God so that we become attached to things of this kind to an extent greater than is necessary. But the divine law was given for this chief purpose: so that man might cling to God. Therefore, it does pertain to the divine law to order man in regard to his love and use of bodily and sensible things.
2 Again, as man’s mind is subordinated to God, so is the body subordinated to the soul, and the lower powers to reason. But it pertains to divine providence, of which divine law is but a rational plan proposed by God to man, to see that individual things keep their proper order. Therefore, man must be so ordered by divine law that his lower powers may be subject to reason, and his body to his soul, and so that external things may subserve the needs of man.
3 Besides, any law that is rightly established promotes virtue. Now, virtue consists in this: that both the inner feelings and the use of corporeal things be regulated by reason. So, this is something to be provided for by divine law.
4 Moreover, it is the function of every lawmaker to determine by law the things without which observation of the law is impossible. Now, since law is proposed to reason, man would not follow the law unless all the other things which belong to man were subject to reason. So, it is the function of divine law to command the submission to reason of all the other factors proper to man.
5 Thus it is said: “Let your service be reasonable” (Rom. 12:1); and again: “This is the will of God, your sanctification” (1 Thes. 4:3).
6 Now, by this conclusion we refute the error of some who say that those acts only are sinful whereby one’s neighbor is offended or scandalized.