Is it time to pull out? Fucking hell fella what kind of question is that?
No one knows, if they did they wouldn't be on here. Stock markets, whether invest through ISA's or straight forward UT, OEICS are a gamble. If you're mate is worried about losing more money switch it over to a less adventurous fund, but the problem with that is when the markets do recover he will not maximise his potential gains.
ISA's are a very tax efficient way of investing, so if he pulls out of his ISA where's he going to put his money? On the high street? In that case the lack of potential returns in better times rears it's ugly head again.
As others have said if he doesn't need his money don't surrender it, just look at the other funds available. You haven't said when he invested and over what period he's lost this money, but don't forget that ISA's (stocks and shares based) are medium to long term investments, it's only a paper loss at this stage, might be a time to be brave and ride the storm out.
The size of the investment is a factor as well. If it's £30,000, I'd be putting more in. If it's only £3000 I clearly wouldn't