I can understand both sides of this issue.
Forrest Cavacco's and Oliver Peck's opinions are shared by most of the tattoo artists I've spoken with over the years--that a tattoo artist should have at least one tattoo so that he/she will know what his/her client is experiencing. And since this issue hasn't been mentioned previously on the show (that I can remember) I'm guessing Peck wouldn't have said anything (not on camera, anyway) if Cavacco hadn't said something first. I know I wouldn't get a tattoo from an artist who wasn't tattooed, but that's a personal choice.
However, Jamie Davies' opinion is equally valid. It's his body, and if he hasn't yet found the right art or the right artist he shouldn't be tattooed. And he's right about the level of hypocrisy that was openly expressed; people who are often judged just because they have tattoos shouldn't judge someone just because they don't. There's an old saying that goes, "The only difference between tattooed people and not-tattooed people is that tattooed people don't care if you're not tattooed." I still believe this is true in most cases but, apparently, it doesn't hold true if you work in the tattoo business.
It's unfortunate that this issue was raised in an episode in which the artist with no tattoos was sent home. If it had happened during any other episode it would likely have been nothing more than a few passing comments, and back to business as usual afterward. As it is, it's obvious some people believe Jamie was penalized for not having tattoos.
Regardless of the actual reason for the judges' decision, I agree with it. Sarah's decision to add that black background element wasn't a particularly good one, but the rest of her tattoo was better executed than Jamie's. I think most people are against the decision because, between her comments and her breakdowns, Sarah doesn't come across as a particularly likeable person, and I can't disagree. But I also think she doesn't have the talent and/or skill to be a "tattoo master" and will likely be sent home soon, probably in the next episode.