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 actually are. We do not worship the crucifix. We use it as a reminder of Jesus suffering and death for the sins. We don't worship the fish. We display it as being 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 they may be role-models for us to emulate.
Dating back to once the Ten Commandments received to Moses, idolatry in the Old Testament was understood to be the worship of idols or images. It's the worship of not God that's wrong and sinful. The mere images, symbols or icons aren't the problem.
A great illustration of this within the time of Moses is the Brass Serpent. God commanded Moses to create this Brass Serpent and lift it high for stopping any Israelite who looked at it of snakebites. I repeat it had been God who commanded Moses to make this picture. Later ever, King Hezekiah destroyed the Serpent since the Hebrew people had been burning incense into it in worship. The symbol had eventually become an item of idolatry. See the difference?
When God gave commandments regarding idolatry he meant it to be understood in its most literal form. According to the Bible, most idolaters really believed that their idols were gods. That isn't so today with Catholic Symbols.