Ridicule of the subject holding a belief is a common way to push back against harmful ideology, and it can be quite effective--when the mindset is based is based on an elevation of the subject holding it. However, the incel mindset is not based on an elevation of the subject, but rather a degradation of that subject. The whole ideology is about placing high value on that which the subject wants (either in and of itself or as a status indicator) but cannot obtain, and furthermore viewing themselves as inherently defective due to this lack. The fact that incels often take this out on women is just one way in which toxic masculinity can manifest. The idea that men who have sex with women or who women are attracted to are somehow less likely to commit misogynistic violence is not, in any way, reflective of reality or feminist. And yet this is a key way that mainstream feminism often positions itself in opposition to incels, reinforcing, as they do, the centrality of the importance of sex as a measure of value.
A big problem with a lot of ridicule about incels is that it implicitly buys into the same belief set about sex. It's a self-denigrating mindset, based on the subject's inability or perceived inability to attract sexual partners. And so ridicule based on denigrating the subject based on their inability to attract sexual partners is an agreement with that belief set, not a disavowal of it. All of the 'chad' and 'incel' memes are not only ripped straight from incel ideology themselves, but typically express the same values even when they are being used by leftists.
So what would an actual opposition of incel beliefs look like? Well, to determine that, we have to look at what the belief set actually elevates: not the incel, but the act of sex as an all important determinant of individual worth and societal status. Not the incel, but the idea of nature over nurture, the idea that there's some defect (often physical) that makes the incel inherently unable to attract sexual partners, a buy in to genetic determinism, a sort of modern-day phrenology. These are the ideas that must be ridiculed if one wants to ridicule the ideology of incels.