I don't really get this.
Sample all you want if it makes your live set better.
The boundaries between djing and live sets are blurring more each year with developments in technology.
If you are sequencing other people's loops live is that a live set or a dj set? A la Hawtin?
Wouldn't tell him to f/ck off and die for using other people's loops. Might give him a slap and a once over with a pair of clippers mind but...
To me a live set is anything that involves the creation of new music on the fly, with the potential to go in many different directions. So long as its done well I have no problem with people using other people's loops.
Tim Exile would always play about 15 anthems in 5 minutes all cut up and mangled, just to hype up the crowd. It worked brilliantly. Do it for for effect, play other people's loops to make an impact.
Passing other people's talent off as your own is shoddy. Using other people's work constructively for effect can be dynamite.
Ramble ramble...