For those of you not familiar with this controversy, there is a summary (from this article)
1. Captain America, a hero created by two Jewish men on the eve of World War II to fight Nazis, is revealed to be an agent of Hydra, a terrorist organization which essentially serves as Nazi proxies in Marvel Comics and is explicitly a splinter group of the Nazis in the MCU.
2. Critics and fans who take issue with this story are told to “wait and see,” dismissed as bullies, and/or parodied with a group of “social justice warrior” villains in writer Nick Spencer’s other Marvel vehicle, Captain America: Sam Wilson. (Bonus: a black character apologizes to a white character for being a civil rights activist. Wow.)
3. Rare Jewish comic book character and in-universe Holocaust survivor Magneto – also created by Jewish men – joins Hydra.
4. It’s revealed that in the Marvel Universe’s original timeline, the Allies actually lost the war, and the good guys used a Cosmic Cube to ensure victory (but apparently considered the death of 11 million people in concentration camps, including 6 million Jews, to be acceptable losses, yet should still be viewed as “the good guys”).
5. Hydra Cap is pictured holding Thor’s hammer, implying that despite his Hydra affiliation he somehow remains worthy. It’s worth noting here that Norse mythology and iconography like Thor’s hammer is a particular favorite with white supremacist groups.
6. Perhaps worst of all, Marvel decides to drum up excitement over Secret Empire with a “fun” marketing campaign wherein comic book store employees wear exclusive Hydra shirts. Because who doesn’t love being blindsided by low-key Nazi cosplay on a Wednesday afternoon?