I guess you have no issue with Patreon and Mastercard deciding which business you can give money to either ? Not so diffirent from banks refusing to serve cannabis stores, or pornstars.
Youtube is trying to stem the outflow of advertisers who've clearly stated that they don't want to be associated with certain kinds of content.
There's an argument that perhaps Youtube should provide the ability for content creators to provide their own Ad Network integration, if Youtube is unwilling to provide that monetisation themselves.
However, creators are free to source their own advertising deals and directly incorporate those into their videos - see just about everyone advertising Audible, Squarespace, Dollar Shave Club, Brilliant, etc.