Gertrude,
I would be interested to know the extent of the "freaking out" - did he/she say in what way they "freaked out"? Some people sit quietly and freak whilst others get more physical and it's those latter ones you want to avoid taking up. Even as an instructor I would be very cautious about taking someone up whom I knew had a history of "freaking out" and would simply question their motives for wishing to subject themselves to that same trauma again because to my relatively sane mind it doesn't add up, eg; I hate spiders and would not wish to touch one!
The bottom line as already highlighted by Mad_Jock is that if there's any doubt then don't do it.
VFE.