I would tell them... That you want to do everything you can for Israel and your Jewish Brothers! And by joining IDF it's the closest your going to get to helping.
I agree About newaza, and having to learn every term. When I did pure Judo{for a short time} the first time I did newaza... I beat the top student within three seconds. I put him in an ankle lock, not knowing it was an illegal technique.
I do believe Grappling is important though, but you have to take into count your environment in the street. You have walls, concrete sidewalks, alleys with broken glass. Plus in the street, or in combat you have your teeth, finger tips, etc. So some sport techniques can be defended rather easy! But you need to know what your opponent is trying to do.