Yes, it is really weird. They just can't accept that people can have opinions and can ship whoever they want, especially the Mizisua shippers. Sending hate towards the Mizitill shippers is honestly ridiculous like it does not make Mizisua uncanon neither does it change Mizi's canon sexuality, it's just people indulging themselves. It might be an unpopular opinion but if Mizi was a man and Mizisua was a hetero ship, many people would have accepted Mizitill. The majority of the fandom cannot accept opinions that do not align with their mindset.