"music is not property, because it is not tangible". No, music is tangible, it is written on paper, like a novel, with symbols being the musical notes instead of letters. When played, music is vibrations of molecules, so it is very tangible.
"piracy does not hurt profit". If one produced a song that was 100% pirated, profit would be 0. So, piracy does hurt profit.
"a pirated song is not a lost sale". It is a lost sale, because it denies profit to the owner of the song.
"copyright exists for the promotion of arts and culture". No, no matter how it is being said, copyright exists to protect profit. Encouraging an artist to create more works is only meaningful if the artist can make a profit from its works in order to sustain him/herself.
"piracy is not immoral because corporations are evil". But you could fight the evil corporations by not using/buying their products, which you obviously do not do. So, that is just and excuse for not paying.
"I may pirate things, but I always buy them later, and most other people do so". Pirates who do not buy the products later will not say so in any poll, or on the internet.
"copyright should not exist because it hinders the promotion of culture". No, it does not, because, by your own admission, you are willing to pay for culture.
"before recording was possible, musicians earned a living only by live performances". No, they did not, being musicians was their hobby, they all had jobs. Those that did not have jobs were protected by the weathy, mostly royalty or church.
"copyright should only be for 15 years, anything beyond that is stupid". No, it is not. You would pay money for a 30 year old car, why not for a 30 old song?
"artificial scarcity should not be allowed". The ability to copy a song does not mean that scarcity is artificial, because before the copy, the song did not exist. Artficial scarcity is when a product does exist but it is not being sold in order to keep its price high. In the case of a song, an instance of it does not exist before being created.
"piracy is out there, the internet cannot be stopped". Nuclear weapons are also out there, shouldn't we make an attempt to stop them? the availability of something does not make that something legal or good, just because it exists.
"why should we pay X dollars for a song, when the cost of reproducing it is almost zero?" because that is what the song's creator wants, and the right to sell one's product at the price he/she wants is a fundamental principle of our economic system. If you find the price too high, you can ignore the product or negotiate a lower price.