I wouldn’t call a conference on Marxian economics “equivalent” to one on homeopathy or UFOs. Those conferences are not typically held at accredited universities, with the papers submitted and reviewed by likewise accredited and practicing professors and other academics. The people involved in conferences on homeopathy, creationism, and the like are overwhelmingly from outside academia, with no relevant higher education or with degrees obtained from unaccredited diploma mills. Most of them don’t even make a pretense of going through peer review, are not held at or sponsored by any recognized institution of higher learning, and support a community of “practitioners” with an obvious profit motive.
Now, I’m not saying that because Marxian economics is studied by academics, that it must be true. (It’s certainly possible to point to some examples of entire fields of sham science endorsed by academia.) I’m just pointing out that the infrastructure and methodology supporting it isn’t as shady as you make it out to be. If Marxian economics really is a crackpot theory, then it’s done a hell of a better job of disguising itself with the trappings of academic legitimacy than homeopathy, ufology, or creationism ever has.