At the risk of being even more boring than usual, I'll attempt to clarify my views.
1. My first post was in response to Parser's "If you wish to call yourself fluent in English, I suggest that you try to understand the use of "whom" to the best of your ability".
As (at a guess) over 80% of British people are both fluent in English and completely ignorant of the usages of 'whom', I think that Parser's advice imposes an unnecessary strain on some learners. I should perhaps have added the part underlined to the final sentence of my first post: "I see no point in a learner of BrE attempting to master what is alien to many native speakers."
2. As many younger learners wish to be able to converse in natural language with other young people, then insisting on whom can actually disadvantage them (see #3, below). When (if) they wish later to be able to use more formal language then they can, just like many native speakers, learn to do so.
3. I do not advocate denying the existence of whom or claiming that its use is incorrect. When learners who have been previously taught to use it correctly, then I do not try to make them change to who in all situations. I do, however, point out that it can sound very strange in some situations. Most young native speakers would find, for example, "With whom did I see you at the dance last week" most unnatural.
4. With adult learners who may be using the language formally, in speech or in writing, then of course I help them use more formal constructions, including whom. I also cover it in more depth if I know that my learners will be using the language in AmE areas. As Nikki suggested, many Americans use whom naturally; my arguments for not obliging students to learn an unnatural form are not valid for AmE.
5. When the learner's L1 has subject and object forms of the relative pronoun, then I make more use of whom, as I have found that this helps the learning process. However, I still do not encourage its use in informal situations.
I must stop before this becomes even more tedious.