Tattoos
For me tattoos are not necessary and I don't think they're a good idea. On the other hand I think one needs to approach getting a tattoo with prayer and referring to the Bible what God has to say about it in there. You also need to think about for what reason are you getting a tattoo. Are you getting a tattoo for Jesus Christ, or are you getting a tattoo because it's popular and cool and makes you fit in? How long before you are doing other things that are cool and popular and makes you fit in but are contrary to what God does say in the Bible. It's always a slow drift, a little here and a little there and before you know it you think a bible believing Christian is the enemy in the way they think, talk and live. So I think careful consideration is required, for what reason am I getting this tattoo? For what reason do I have a desire to get this tattoo?
The Christians have Egypt have been tattooing themselves for centuries. The world's oldest tattoo parlor is a tattoo shop run by an Egyptian Christian family in Jerusalem that has been in operation since middle ages. It was established for Egyptian pilgrims coming to Jerusalem.
Why do they tattoo themselves? In the 7th century the Muslim armies conquered Egypt, the indigenous Christian population which had been there since the time of the Apostles (the Church in Alexandria being one of the most ancient and important centers of Christianity, and which was established by St. Mark) wanted to preserve their identity in an increasingly Muslim world in which they found themselves. So, they would tattoo small crosses onto themselves, including their children, so that their Christianity would always be permanently on display on their bodies. Even if someone kidnapped a Christian child, that child would still always have the mark of the Christian faith on their body, a reminder of who they are and where they came from.
I also think that your slippery-slope argument is a bit fallacious. As one could easily apply that to conceivable scenario. But then I have seen people say that watching Star Wars or Harry Potter is a slipper slope to witchcraft and Satanism, so really it does get applied to nearly any scenario.
Rather than a slippery slope; wouldn't it be more prudent to simply emphasize faith and Christian discipleship through good works? Whether or not someone gets a tattoo, or what music they listen to, or what movies they watch, games they play, clothes they wear, food they eat, it's all just irrelevant really and really boils down to one's conscience.
I'd argue that more damage is done to those immature and young in the faith when they are given a laundry list of meaningless rules that God certainly does not expect of them, and their Christianity becomes identified with those meaningless moralistic rules--rather than it being about Jesus Christ, His Gospel, and the call to Christian discipleship.
-CryptoLutheran