The old cliche, "That's the way it's always been," or the even more common "Everybody does it" are no excuse for sinfulness.
There is a story of a man who comes to a rabbi and, after recounting a long catalogue of misdeeds, excuses himself by saying, "But everybody does it," to which the rabbi retorts, "Hell is big enough for everybody."
–Rabbi Adin Steinsaltz
From "Soul Searching" p. 21, in The Strife of the Spirit by Rabbi Adin Steinsaltz