Well...that was kinda my quetion to begin with. Can he be held here until he is deposed? If not, you would be right. If so, this will get interesting.
Yeah, and I already told you that he can't. At the very least, they would have 20 days to respond to the complaint. No judge is going to force a foreign national to stay in the US to answer a civil lawsuit. Even if they got the VdS in court, they could just tell them to take the default and let them go home.
Lets say that you got sued. The plaintiff wants to depose you. You refuse. They go to court. The court will compel you to be deposed. You again refuse. The court will impose a fine on you. You again refuse. At this point, the court will, at most, bar you from raising a defense.