Are you saying that listening to youtube recordings of music is stealing from the musicians?
Simply listening to the music is not copyright infringement. But making copies of music and distributing copyright protected material without permission is copyright infringement. (Unless protected by fair use or other exception). You can read the law
here if you care to.
The overwhelming majority of stuff music on youtube was uploaded by regular folks without the copyright holder's permission. The uploading of entire songs, music videos, albums, and movies constituted infringement in the majority of those cases. Downloading that stuff to your hard drive also constitutes infringement in most cases. The advertisements on youtube benefit YouTube and Google and not the musicians or even their labels.
Google is protected by the DMCA (Digital Millenium copyright act) from being liable for the music that users upload provided that they take the music down as soon as the copyright holder complains about it. At least that is the case under US law.
I'm not going to tell you how to feel about your own activities with regards to copyright infringement. If you believe the law is unjust, or that you are sticking it to the man, or that copyright is simply corporate welfare, then that's what you believe. But I can point out what the law says.
You don't seem to have that kind of slippery morals. So for you it might be important to know where the advertising money goes. It does not go to the copyright holder with the exception of those cases where the copyright holder has a deal with Google. In most cases, there is no deal.
And no, I don't just play lawyer on the internet.
Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)
The apathy of the people is enough to make every statue leap from its pedestal and hasten the resurrection of the dead. William Lloyd Garrison.
If there is no struggle, there is no progress. Those who profess to favor freedom, and deprecate agitation, are men who want crops without plowing up the ground, they want rain without thunder and lightning. Frederick Douglass