Just a couple of things ..
Isn't this a bit like the petty theif pointing the finger at the bank robber and telling him how bad he is? Theft is theft, crime is crime.
It's all illegal .. it's splitting hairs I think.
Secondly, if the argument is that we're somehow robbing arcades by not putting money in their new machines. Then every person that plays Galaxian or Space Invaders is killing off the trade of those that beautifully restore these machines. The price of these has come down, and many restorers will simply throw the towel in. Old or new .. makes no difference, it's affecting someone. If you ever visit RGVAC or some of the other arcade forums, you'll see that some people despise MAME for that reason.
I think MAME is awesome, totally amazing .. but I'm not under any illusion about exactly what it is, what I'm doing, and who it's affecting.