This sort of trademark dispute happens all the time outside the music business too. A key issue is likelihood of confusion: if you are a fan of Ghost (the band) and heard they are making a Ghost-branded liquor, and if you want to support the band (or just think it’s cool) and buy that liquor, might you be confused and accidentally buy the Ghost vodka instead? Particularly since its skull logo looks a lot like at least one Papa? Maybe?
If so, and if the band (or, Tobias’s company, technically) has legally trademarked “Ghost” for the sale of spirits in the EU, then that’s a real basis for a case. That said, the vodka makers say they came to market first with the Ghost brand, so we’ll see whether they have a good argument under EU law that Tobias’s trademark is invalid as to liquors and spirits (as distinct from music) due to the prior use of the mark since 2015. I don’t know enough to handicap this. The aggressive, mocking tone coming from the vodka makers suggests they have no interest in taking a license or paying a royalty, so a collaboration seems pretty speculative at this point.
I may be in the minority here but I think, because most artists don’t make any real money from the sale of their actual music anymore and also cannot tour these days, trying to protect their merch IP as a business asset is very reasonable. If Tobias has a valid trademark and the vodka infringes it, then he should win, and he’s not “petty” for enforcing his commercial and creative rights.