In almost every artist nature is inborn a wanton and treacherous proneness to side with the beauty that breaks hearts, to single out aristocratic pretensions and pay them homage.

Mann is diagnosing what he sees as a recurrent moral weakness in the artistic temperament: an attraction to dazzling, socially elevated, or “aristocratic” forms of beauty even when they are destructive (“beauty that breaks hearts”). The artist’s sensibility, in this view, is not automatically democratic or ethically reliable; it can be “wanton and treacherous,” instinctively siding with glamour, refinement, and pretension rather than with ordinary goodness or truth. The line also implies a critique of aestheticism—art’s tendency to grant prestige to surfaces and hierarchies—suggesting that the artist’s homage to elite beauty can become a kind of complicity with social power and emotional harm.