I will just bet that what your husband's REAL beef with the nanny is that he doesn't think she is intelligent enough. He probably doesn't want to consider that this is what he's reacting to, so he makes it all a personality thing.
Because of the language issue, there's not a way to gage her intelligence. But I will say that there are people who don't have much education in the formal sense, who are wonderful at child-rearing and have a ton of common sense. There are educated people who appear to not know what the heck they are doing with kids and you wonder how they get through the day with their lack of common sense!
If my husband felt this way about the main caregiver of my children, I admit that I would find another caregiver. Nothing you say is going to change his mind. He considers that he is paying good money for someone - he wants that person to not only be a babysitter, but also a type of "governess", for lack of a better word. He wants someone to challenge the children's brains, push them to exercise, make them "think" when they are bored.
My SIL did the same thing, S.. She had a nanny for several years, but there were things that really bothered her about the nanny. I think the woman just got complacent in her job, though I'm not sure that I'm right about that - maybe she was just lazy. She would only take the kids out to the park if my SIL told her to. She NEVER wanted to take them to the pool - it was like pulling teeth to get her to get INTO the pool with them. All she wanted to do was sit with the other nannies and talk. My SIL was BIG into physical exercise, lots of fresh air, sports and all of that. This nanny was big into sitting...
So yes, she hired a different woman to take care of the kids and never regretted it. She may have paid more, I don't know. She did not go the route of hiring a non-native speaker. There was never an issue of a communication problem between her and the nannies or the nannies and the children.
Tell your husband that what he really wants is a nanny with a childhood education type of degree and training. Tell him that this will cost more money. Tell him to find people to interview. When you put the onus on HIM to find candidates to interview, he will either put up or shut up. Leave it up to him.
I know you feel that an attack on her personality is the problem, but that doesn't mean that he is wrong in feeling that he wants a different personality taking care of his kids. The real issue is that he has to go back to square one to find someone who does a fine job AND has the personality traits he wants. It's not an easy thing to do. However, rather than let him push you into the role of finding it, and then b*tchin' to high heaven about who YOU chose, make HIM find her instead.
Good luck