Yes, we refuse to help people who are objectively attacking the network, wasting other users resources and harming their privacy.  Beyond it being harmful to bitcoin and bitcoin's users, knowingly assisting in this activity might make a participant a target of torts from harmed parties or even subject to criminal prosecution in jurisdictions with expansive computer crime laws.

Why people think that its casually okay to attack the network, and think there is any chance that standard Bitcoin software would come with a user exposed switch to make it try to use a substantial fraction of the network's total capacity is beyond me.

That isn't going to happen; and users should be highly wary of the competence or ethics anyone who ships software that does that (after all, if might makes right then why not also have the software backdoor your computer?-- if it's possible to do, it's okay, by the logic presented here, no?). The fact that someone don't have any ethical qualms about the resources of other people that they waste or the privacy harm most of these efforts are intended to create, nor do they have the most basic software engineering experience to understand the requirements and ramifications of a software change; doesn't create any obligation on my part to compromise my own integrity and aid in these activities.

And sure, sufficiently software-competent people can technically modify the software or write their own which behaves aggressively; but fewer people doing it is an improvement (less resources wasted) even if it is not possible to make prevent it completely. This isn't the only thing that is done with respect to this kind of abuse, like in many things a layered response is important, the first is avoiding cases where thoughtful and ethical people do not accidentally abuse the network-- and making it clear what behavior is abusive--, then social, technical, and legal measures can be employed against those who remain. (All of which are continually being worked on by many people).