Wagner scholar Barry Millington has written that anti-semitism is woven into the ideological fabric of Wagner's opera Die Meistersinger, and that the representation of the character Beckmesser incorporates unmistakable anti-semitic characteristics. See Barry Millington, "Nuremburg Trial: Is There Anti-Semitism in Die Meistersinger?" (1991).
Millington claims that Beckmesser, in his serenade in the second act of the opera, recalls synagogue chant.
You be the judge.
I suppose we will never know what Wagner intended; Wagner's anti-Semitic intent in Die Meistersinger is not something that can be proven. It's a matter of interpretation and inference. And we are free to speculate. Whether Wagner's characterization of Beckmesser is anti-Semitic is similar to the question of whether a person who incorporates words and phrases in his speech such as July (Jew lie?), liar, liar pants on fire (the notion that Jews are liars is, arguably, an anti-Semitic stereotype), and oy veh is motivated by an anti-semitic animus.
We're permitted to have our own opinions. I would refrain from concluding that Barry Millington's interpretations of Wagner's possible anti-Semitism necessarily indicate that Millington is psychotic and potentially violent, however. But hey, that's me.
By the way, Charles Rosen rebuts Millington's arguments in "Wagner's Anti-Semitism." The New York Review of Books. Nowhere does Rosen suggest that Millington is mentally disturbed because he believes that Wagner's Die Meistersinger seeks to advance an anti-Semitic agenda.