The commonly accepted argument for shaming alternative medicine use is that the counterfactual is a patient accessing mainstream medical care - even though some alternative medicines are more or less harmless, or just less effective than clinical best practice - that's opportunity cost.
Currently effective altruism is framed as an improvement upon naïve altruism, but for the most part, a lot of people don’t find naïve or ineffective altruism that problematic. Good is the enemy of the better. Who's upset at someone for donating to charity?
Why don't we stigmatise naïve, ineffective altruism. Well, the danger is reducing the net good done, for it may turn some off doing a good deed altogether. And, hostility can damage movements, individual reputations and one's own peace of mind.
Could we, with a nuance and tact, institute a social ''stick'', to complement the many carrots that draw people to effective altruism, by shaming harms that are reasonably foreseeable.
That doesn’t sound too harsh does it? Reasonable person tests are already a common legal standard.
At the small scale, when you say offer to help your sister move home and drop an expensive vase, the harms aren’t reasonably foreseeable, and therefore, that wouldn’t be fair game to shame as pathological altruism, unless you are clumsy. To generalise, it was an unlikely and difficult-to-predict outcome of good intentions.
To contrast, if your brother has a methamphetamine addiction, goes into withdrawal, and you supply him meth to make him feel better, irrespective of your good intentions, that is pathological altruism.
Installing another play pump after seeing that it doesn’t work well (whether by practice or access to more widely available EA guidance, dropping your sister’s vase after smoking that meth with your brother - say it with me: pathological altruism.
One thing that's lacking a bit here is a concrete path to impact, and how this strategy would be integrated into current effective altruist outreach efforts. It's a very abstract suggestion.
Because of the large differences in effectiveness between different interventions, I'm not that worried about this issue.
One of the first definitions I see when looking up pathological is “involving or caused by a physical or mental disease” (albeit along with “compulsive, obsessive”), and the connotation of “pathological” is really negative and insulting. EA already faces accusations of being elitist and insulting to other causes, which may undermine its appeal to some people, and I am fairly skeptical of the idea that this “social stick” (as you call it) will actually be effective at persuading people who don’t already share your point of view.
Therefore, I am really averse to calling things like playpumps “pathological altruism.” There are a few things which are quite actively and (this is important) clearly harmful and thus probably warrant condemnation: for example, some situations where someone is enabling a drug habit. However, society already does have norms against many of these things, and there doesn’t need to be some new “EA social stick.”