Questions always arise as to whether the use of Catholic Symbols is really a type of idolatry. Usually it is because the questioner is not altogether acquainted with what these symbols really are. We do not worship the crucifix. We use it remember of Jesus suffering and death for the sins. We do not worship the fish. We display it as a proud emblem in our Christianity. We don't worship the statues of the saints. We use them to point out their wonderful lives so that they might be role-models for all of us to emulate.
As far back as once the Ten Commandments were given to Moses, idolatry within the Old Testament was understood to be the worship of idols or images. It is the worship of anything but God that's wrong and sinful. The mere images, symbols or icons are not the problem.
A great illustration of this in the duration of Moses may be the Brass Serpent. God commanded Moses to make this Brass Serpent and lift it high for stopping any Israelite who looked at it of snakebites. Once more it was God who commanded Moses to make this picture. Later in history, King Hezekiah destroyed the Serpent since the Hebrew people had been burning incense into it in worship. The symbol had eventually be an item of idolatry. See the difference?
When God gave commandments regarding idolatry he meant it to be understood in its most literal form. Based on the Bible, most idolaters really believed that their idols were gods. That isn't so today with Catholic Symbols.