I think it's important to remember that there's a difference between being involuntarily celibate and being 'an incel'. Some people are just socially awkward etc. but do not hate women and blame them for all their problems; others have become bitter and hateful and they are what most people associate with the word incel. I doubt anyone is truly proud of being the latter type of incel, but they may be proud to be part of that 'community'. These people are social outcasts and have formed a group of other like-minded people, finding acceptance where perhaps they haven't found any before. I am speculating, but I would say that they could be proud of being part of that group / having that label, while at the same time hating actually being involuntarily celibate.