in case of judo and boxing, most people talk about the purpose it has NOW, then he might be right. ground fighting in judo was limited more and more over time and (i saw around here) the grappling techniques of boxing were exluded also (didn't even know before that there were any). so these styles would "evolve" to specialized sports like we know it today. for olympic gold medals or whatever championships...
in case of krav maga, indeed, this is not just for taking weapons away. what gave him that idea?
its for surviving in general.
when someone isn't sure but wants to train something helpful, i'd say start with kickboxing. its the basics of fighting, no belts, no asian terminology, no forms, no "complicated" grappling... and its techniques are like or included in muay thai, karate, taekwondo, ju jutsu, hapkido, krav maga etc., so one can switch to an other style everytime later.