When he does propose the plan to the Basterds, he tries too casually to underplay the importance of the radio operator. His homosexuality may have done a lot to push him to betray his country for a land that didn’t criminalize his behavior.
Hans might be referring to the plight of a gay man under Nazi rule. In the opening scene, Hans Landa tells the farmer “I am aware what human beings are capable of once they abandon dignity.” No reasons given, but this a Tarantino film where every line is intentional.
Some may say that disproves my theory, but it’s not like gay men don’t hang out with women a lot. In about three different instances, the subject of him being a womanizer is brought up. For the time period and his age, this is unusual. He’s a very high-value man with no family. Some internet posts here and there have brought this up, but I wanted to drive home the point because I get more and more confident about this on each rewatch. Edit: Spoilers below! Edit 2: Evidence linked