I think it's clear that if I reword:
"I do not believe it is ethical to accept gifts from those who | whom he has not conducted business with."
to be:
"I do not believe it is ethical to accepts gifts from those with whom he has not conducted business."
that "whom" is correct. But what about in the first example, still "whom"? Sounds wrong to me...
[QUOTE=BobSmith;846852]
"I do not believe it is ethical to accept gifts from those who | whom he has not conducted business with.
***** NOT A TEACHER *****
(1) I believe that we recently had a discussion about so-called "stranded prepositions."
(a) That is, the only "wrong" sentence would be one that used "who."
(i) I believe, therefore, that you have three choices:
(ia) It's wrong to accept gifts from those with whom he has not conducted business.
(ib) It's wrong to accept gifts from those whom he has not conducted business with.
(ic) It's wrong to accept gifts from those he has not conducted business with.
(2) I believe that (ia) is very formal; (ib) is an example of a "stranded preposition";
and (ic) may perhaps be the most popular, for it avoids the need to use "whom," which
most people find much too formal (besides requiring too much effort to pronounce).