All the arguments along these lines with respect to scalpers get caught in the "is-ought" problem [1]. You are describing the economic situation and saying "This is the way things are at the moment, therefore this is the way things ought to be". It is a leap that you don't really justify.
If people want to take a libertarian approach, why don't you say it is the person selling the tickets prerogative to do every legal thing in their power to limit prices. It is their show after all.
It would be as if I started selling piggy back rides to my friends for $10. When some random guy realizes my friends really like piggy back rides (for whatever strange reason), so he buys all my piggy back rides. I'm all booked. He then turns around and tries to sell them to my friends for $20. What the scalper apologist arguments are saying is that any attempt by me to tell this scalper to get lost is somehow wrong, because I am disturbing the natural order of things. It doesn't take into account that I care who I carry.
To be clear, I'm not saying artists only selling to "poor people" is the sole right way or something of that sort. I'm just arguing against saying that second price auction is the only way to do things.
[1] https://en.wikipedia.org/wiki/Is%E2%80%93ought_problem