I think it's a really cowardly approach.Austin Walker recently talked about how he would not debate with known insividuals so that they would not benefit from his platform.
I think that's a pretty solid approach.
There are people who watch these discussions who are 100% entrenched on either side of the people involved they won't change their mind, that's why you aim for the ones in the middle who when they are exposed to people's arguments about hateful/toxic/damaging ideas being debunked/beaten will be spared from going alt right/gg and so on. Hell you might even grab some from the actual bad side and convert them.
Now maybe Austin Walker doesn't want to put the effort in to educate himself enough to be able to defeat arguments/stances from those people and thus thinks it's irresponsible to platform them and that's perfectly fine. Saying platforming people with horrible views only leads to them benefiting is 100% wrong if you put in minimal effort.