I agree that without some very valid reasons, your husband sounds like his behavior on this is very selfish and silly.
That said, I agree with you and your husband that business and family generally don't mix well (kind of like loaning $$$). Does he feel like you're disregarding his opinions about the business to keep peace with your family? Does he think there are sides, and you're not on his? For the most part, it seems like men are a lot more level-headed about this stuff than women are, and he may believe that you'd see things differently if you were in business with a business partner, rather than a family member.
Also, when your husband and your father (or other family members) are in the same room, does your husband feel like he's being judged or belittled or ridiculed?
I've had to tell my mother on several occasions in no uncertain terms that she WILL be nice to the man in my life, and that if she has a problem with him, she WILL either keep it to herself or speak with me privately, but she is NOT to speak her mind without regard to my feelings or my SO's. Thankfully, by the time I met my DH, she pretty well understood that I will not bend on this. (I know that sounds harsh, but one morning, I walked into my parents' kitchen to hear her telling my on-again, off-again BF that he wasn't good enough for me because of his divorces and drug history. It was true enough, but at 27 or 28 years old and visiting from 2000 miles away, it was NOT my mother's place to have this discussion with him. Sure made for an uncomfortable flight home.)
I guess I'm thinking that if either of these things is going on with your husband (even if it's just in his mind), I can understand where he's coming from, and I probably wouldn't want to visit them either.
Is he good to you in other ways? Or is he always petty and selfish? If this is the ONE area where you'd say he's unreasonable and ridiculous, I think it's probably a case in which you need to choose your marriage over your parents. Go to FL by yourself. Spend holidays at home with your husband. Don't go to his family stuff if you don't want to, but if you like his family, then don't deprive him and them and yourself just on principle.
But if this is just one example of his generally selfish and childish behavior, I think you should probably seek marital counseling and get to the bottom of it. If you married the wrong guy, then figure it out now.
__________________

|