Unfortunately a common problem almost always men wanting to tell women what to do.
Hopefully they will learn - if not they will generally leave
In this situation just drop him - generally that's a REALLY good lesson.
It helps to have female yudansha in the dojo. Having someone 4'11" and 100 lbs put them *through* the mat has a way of teaching even the big guys a little respect....
On the other hand, being attacked by someone much bigger makes a lot of people tense up. Which will of course cause your technique to not work. Which leads to clotheslining and all sorts of other unpleasant behavior on the part of nage.
Remember, it's not uke's fault that he's big and tense. Being big is just genetics, and being tense is just because he's new. Think of it as an opportunity to learn to deal with that kind of energy.