It seems to me there are some other underlying and larger issues going on between you and your husband. If my husband ever came to me and said "hey, why don't we look into putting little Sally into day care just a couple days a week so she can be around other kids" I would not "go ballistic" as you say you did. (not saying I wouldn't take your stance, just that it wouldn't make me so angry). It seems you are both frustrated with each other beyond what this post indicates.
I think what your husband is getting at is that your daughter benefits greatly from being around other kids WITHOUT mommy around and having to be told what to do by someone else OTHER THAN mommy. I don't think this is a bad thing at all.
But, I also think you keeping her home with you and doing what you have been doing is PERFECTLY FINE AND HEALTHY also.
Why would you refuse to budge? Does he? Why can't you two talk calmy about this and come to a compromise? It seems like such a simple discussion.
There is no right or wrong answer here - the problem is the lack of ability to communicate or compromise between you and your husband. I would think he should give you some deference as mom and child-rearer, but at the same time, don't get so angry with him. Realize he is only trying to do what he thinks is best for your daughter, even though he "may" be a little off in his approach.
The point is, this shouldn't be a heated discussion. Save those for when she wants to date.