That statement has more holes in it that a block of swiss cheese on a rifle range. No evidence to support it- you still get exposed to germs, but not in the numbers. An uncompromised immune system doesn't roll over and die before a few score of something, you need a LOT of it. So if you've killed 90% of the germs, your body can smack the other 10% around if they get through your skin and then it will remember what that germ looked like in case it's kin come a calling. (Jeez, that sounds redneck.)

Use of the antibacterials making germs tougher DOES have evidence; that's why I have plain old Ivory. The lye will kill enough.