GamerGate was the first major loss for feminism and SJWs in the culture wars. Who did feminist believe was behind GamerGate and handed them this loss? They stereotyped them as: nerds, men who lived in their mom's basement, neck-beards, failures to launch, game-boys, or just plain old losers. This stereotype was far from true (for one, many GamerGate supporters were female), but it is the stereotype feminist had of their enemy.
And, make no mistake, feminist did consider this group of men enemies. Their defeat at the hands of these men has stuck in their craw ever since. The have never let go of it, and still want revenge. In the word incel they think they have a vehicle.
The definition of incel seems benign (involuntary celibate), but the word has a sinister purpose: to humiliate, degrade, and other a group of people. With othering being the most sinister purpose of all--to separate these men from society and make them untouchables. Consider former Reddit CEO Ellen K. Pao's tweet:
CEOs of big tech companies: You almost certainly have incels as employees. What are you going to do about it?It is a not so thinly veiled attempt to have these men fired from their jobs and make them outcasts--to other them.
Like the N-word, the word incel has no place in society. Rather than argue over its definition's accuracy, we should reject it outright, because its purpose is evil.