Objection 1. It would seem that rites of unbelievers ought not to be tolerated. For it is evident that unbelievers sin in observing their rites: and not to prevent a sin, when one can, seems to imply consent therein, as a gloss observes on Romans 1:32: "Not only they that do them, but they also that consent to them that do them." Therefore it is a sin to tolerate their rites.
Objection 2. Further, the rites of the Jews are compared to idolatry, because a gloss on Galatians 5:1, "Be not held again under the yoke of bondage," says: "The bondage of that law was not lighter than that of idolatry." But it would not be allowable for anyone to observe the rites of idolatry, in fact Christian princes at first caused the temples of idols to be closed, and afterwards, to be destroyed, as Augustine relates (De Civ. Dei xviii, 54). Therefore it follows that even the rites of Jews ought not to be tolerated.
Objection 3. Further, unbelief is the greatest of sins, as stated above (Article 3). Now other sins such as adultery, theft and the like, are not tolerated, but are punishable by law. Therefore neither ought the rites of unbelievers to be tolerated.
On the contrary, Gregory [Regist. xi, Ep. 15: cf. Decret., dist. xlv, can., Qui sincera] says, speaking of the Jews: "They should be allowed to observe all their feasts, just as hitherto they and their fathers have for ages observed them."
I answer that, Human government is derived from the Divine government, and should imitate it. Now although God is all-powerful and supremely good, nevertheless He allows certain evils to take place in the universe, which He might prevent, lest, without them, greater goods might be forfeited, or greater evils ensue. Accordingly in human government also, those who are in authority, rightly tolerate certain evils, lest certain goods be lost, or certain greater evils be incurred: thus Augustine says (De Ordine ii, 4): "If you do away with harlots, the world will be convulsed with lust." Hence, though unbelievers sin in their rites, they may be tolerated, either on account of some good that ensues therefrom, or because of some evil avoided. Thus from the fact that the Jews observe their rites, which, of old, foreshadowed the truth of the faith which we hold, there follows this good--that our very enemies bear witness to our faith, and that our faith is represented in a figure, so to speak. For this reason they are tolerated in the observance of their rites.
On the other hand, the rites of other unbelievers, which are neither truthful nor profitable are by no means to be tolerated, except perchance in order to avoid an evil, e.g. the scandal or disturbance that might ensue, or some hindrance to the salvation of those who if they were unmolested might gradually be converted to the faith. For this reason the Church, at times, has tolerated the rites even of heretics and pagans, when unbelievers were very numerous.
This suffices for the Replies to the Objections.
Source: Summa Theologica (New Advent)