You show one antisemitic person and leap to mainstream.

Well it is 100% mainstream in the MAGA movement:

"Nazi heaven: Inside Miami campus Republicans’ racist group chat"

"The secretary of Miami-Dade County’s Republican Party started a group chat for conservative students last fall — and within weeks it was filled with racist slurs,
including dozens of ways of violently killing Black people. The chat was renamed after what one member described as "Nazi heaven."

"Participants used variations of the n-word, regularly described women as "whores," used slurs to talk about Jewish and gay people and mused about Hitler’s politics."

"You could argue even with some of them Trump executive orders about race he signed immediately after being sworn into office — I think it’s sending a signal that you don’t have to hide your racism anymore" Said one MAGA poster.

In psychology it's known as the false consensus effect.
Since Dope is full of hate he thinks everyone else must be also.

miamiherald.com - Politics government