NTA, and your husband's line of reasoning is incredibly self-centered and petty.

all his reasons boiling down to him feeling excluded and disrespected by it

Where does this type of justification end? If your husband never learned a musical instrument, does that mean that none of your children are allowed to ever learn how to play one because he might feel left out or something?

What about any other hobbies/skill sets that your kids might eventually become interested in? Does your husband have final say over rejecting them because they might be something that he's never done/experienced before?

Your kids will one day be fluent in both languages A and B and they will be better for it. Hopefully you and your husband can then look back and laugh about how silly it would have been to deprive them of that for any reason at all.