I might be jumping in quite late here, but how does the ability to cover some aspect of one's appearance readily, or the lack of that ability, confer moral significance? You said that such a distinction is very important to you. But why is that exactly? What is the morally significant difference between a physician or physician-in-training covering tattoos and a physician/physician-in-training being asked not to use unnatural-looking hair dyes?
One dictates how you dress at work
only, the other dictates what you can do in your own time at home.
In the context of OP (purple tips) or the "blue streak" that you brought up, I think those are pretty easily covered up by temporary dye (unless you have blonde hair) or with certain hairstyles. If most of your hair is an unnatural color, that's another can of worms, and I would argue that that would be considered unprofessional by most people.
Something else that can't be easily covered up and is similar in analogy to the hair color - ear gauges. Even a 4g or 6g is a noticeable gauge and will leave a noticeable hole if the plug is removed. So where would you draw the line?
We can agree to disagree, as the discussion is pretty hypothetical and neither seems to be budging. I just fail to see how you can pick and choose which professional norms to follow based on whether or not they can be covered up. Visible tats are considered unprofessional by many, but since you can cover them up, it's all good! Many, many people think unnaturally colored hair is unprofessional, but since you can't easily cover that up, people should just get over it?
Again, I've never seen a truly temporary hair dye which didn't look worse than having your hair cut with a buzz saw.
As for gauges, you can a) get a flesh-toned plug or b) not worry about it. As you can probably tell from my stance on hair dye, I think people should be able to gauge their ears as well, so long as they are willing to make a clear effort to be well-groomed for professional settings.
I'm not actually drawing a line with these examples. I do have one somewhere (horn implants, forked tongue, etc), and you are right in that I need to seriously consider what my criteria are for drawing it, as right now I am unable to elucidate any concrete criteria. But thus far, with the examples we've hit, my stance on
all of them is: you should be able to style yourself however you like at home, regardless of whether some sign is visible after you groom yourself for work, but you
must still put in the effort when you do get ready to actually enter a professional setting. If you go for a look which is not traditionally professional, you should make a clear effort to address that when you go to work - dyed hair should be neatly groomed and styled so as to downplay the alternative look, tattoos should be covered as much as possible (though it's likely obvious that you have them anyway, the effort to conceal is not unnoticeable), piercings should be removed at work, etc.
If you do not even attempt to prepare yourself for an interaction with somebody, that can be seen as disrespectful. If you simply have more preparation required and the end result isn't quite as pretty (but you clearly took steps to appear as professional as possible given the permanent or semi-permanent things you have to work with), there is not the same vibe of apathy and disrespect.
To me, it is that vibe, the 'I put in effort because I value this interaction' that professional dress is all about, and while you may not end up as uniform, you can still make your respect and effort visible.
Again, perhaps not the wisest business choice, but I don't find such choices disrespectful or irresponsible as long as you make sure you follow through with the latter half.
Finally, you're right. I am fine agreeing to disagree. I'm under no illusion that I can/could ever change your mind, nor that you will change mine. Yet I still learned from this debate (both good and bad things) and am glad to have participated. Discussions like these are not really intended for everyone to come to a consensus, but that makes them no less valuable. So, thank you, and I hope I didn't frustrate you too much (and that you don't think I am completely naive or irresponsible or antagonistic, despite our differences in opinion). To me, in most situations, freedom of choice is one of the most important values, whether the actual outcome is better or not. I firmly believe in people's right to make bad decisions for themselves - patients who ignore their docs, physicians with purple hair, New Yorkers who wish to pursue DM via large sodas, or the avg joe who rides their motorcycle without a helmet - and it bothers me when personal choices are overblown and treated as if they are someone else's issue. People don't get married in order to erode traditional values, and they don't dye their hair in order to make patients feel uncomfortable. If things weren't taken so personally by people who could be 100% unaffected if they didn't fixate on things that don't actually impact them, we could all feel a lot more free in our decisions...and I don't feel particularly obliged to verbally support that mindset, even if I feel forced to go along with it lest I risk personal and financial consequences.
*Note: this is not saying that you guys are the ones taking things personally - your responses all seem to be a reaction to those people who would take a dye job personally*
My young colleague expertly explains here far better than I can as to why there is a reading comprehension section on the MCAT.
a) I've already explained that I see little difference between the two, as the attitude and the behavior go hand-in-hand
b) Unnecessary
c) That joke really only works on those who have yet to take the MCAT.