a pragmatic issue. If someone will get upset by a technique - justified or not - we need to factor that into the decision to use it...discomfort is a sign that the technique is unethical in any meaningful sense

If people get upset by a technique, that is a harm, but if their suffering that harm has good consequences, upsetting them was, all else equal, a good thing to do. So upsetting people is always related to ethics as more than just a sign.

discomfort is a sign that the technique is unethical in any meaningful sense, or merely socially frowned upon?

Unethical things are frowned upon to the extent people feel (at some level) frowning impacts that sort of action; regarding blame:

But determinists don't just ignore the very important differences between brain tumors and poor taste in music. Some biological phenomena, like poor taste in music, are encoded in such a way that they are extremely vulnerable to what we can call social influences: praise, condemnation, introspection, and the like. Other biological phenomena, like brain tumors, are completely immune to such influences. This allows us to develop a more useful model of blame.

The consequentialist model of blame is very different from the deontological model. Because all actions are biologically determined, none are more or less metaphysically blameworthy than others, and none can mark anyone with the metaphysical status of "bad person" and make them "deserve" bad treatment. Consequentialists don't on a primary level want anyone to be treated badly, full stop; thus is it written: "Saddam Hussein doesn't deserve so much as a stubbed toe." But if consequentialists don't believe in punishment for its own sake, they do believe in punishment for the sake of, well, consequences. Hurting bank robbers may not be a good in and of itself, but it will prevent banks from being robbed in the future. And, one might infer, although alcoholics may not deserve condemnation, societal condemnation of alcoholics makes alcoholism a less attractive option.

So here, at last, is a rule for which diseases we offer sympathy, and which we offer condemnation: if giving condemnation instead of sympathy decreases the incidence of the disease enough to be worth the hurt feelings, condemn; otherwise, sympathize. Though the rule is based on philosophy that the majority of the human race would disavow, it leads to intuitively correct consequences. Yelling at a cancer patient, shouting "How dare you allow your cells to divide in an uncontrolled manner like this; is that the way your mother raised you??!" will probably make the patient feel pretty awful, but it's not going to cure the cancer. Telling a lazy person "Get up and do some work, you worthless bum," very well might cure the laziness. The cancer is a biological condition immune to social influences; the laziness is a biological condition susceptible to social influences, so we try to socially influence the laziness and not the cancer.

Society often has good reasons behind its moral classifications.

Use your gut.