Uh... here are my 2 cents.
It is by no means rude not to wear makeup on any given occasion. I personally believe that yes, concealer is makeup, but there are also two sides to makeup. The first side is the "correction/enhancement" side and the second being the "artistic" side. There is nothing wrong with either in moderation.

I feel that there is a problem if people can't accept who they are to the extent that they are not only trying to "correct or enhance" (perfectly fine), but to the point that they try to mask it and make everyone believe that the mask is reality. A lot of people I know who wear it don't go that far, but I have seen some who do (women who won't leave home without their makeup on).

I agree with your friend that the media does put a lot of pressure on women to look a certain way, but I don't believe that people who give into that pressure are stupid in any way. I think it means that there is some social standard that you are expected to conform to, and if you don't, you can be made fun of and ostracism isn't a walk in the park. Now it is true that this won't be the case with every person who wears makeup.

I think that there are irrational people on both sides of this argument: people who think that natural beauty is unacceptable and ugly, and people who think that creative or corrective beauty is sheer stupidity and cowardice from reality.

No one should feel obligated to wear makeup, but in the same since no one should feel obligated avoid it with a red hot poker either.

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After:
"now that's more like it".