People always use Darth Vader as example when pointing out how liking villains is not indicative of someone's morals, but it's for a good reason. Would it seriously be fair to make a broad generalizing and say that liking him automatically means a person supports killing children, genocide, blowing up whole planets, fascism, etc? No, it wouldn't be. Especially if you watched the prequel films and saw how Anakin became Darth Vader wasn't as black and white of a process as one would initially assume.
Or people simply find a monster of a character entertaining. Which has a lot of basis in reality considering how some of the worst people in history- and abusers- managed to gain so much support from others because they tend to be the most likable and charming people.
Or something that people nowadays rarely seem to take into account why people would like villains in general:
The purpose and role they serve in a story. How they effect the events and challenge the main character/s and make them change when they wouldn't have otherwise. How they contrast, or share similarities, with the protagonist/s, and might even make the audience see things differently than they did before. Frollo is one of the most morally reprehensible Disney villains, but he's also considered one of the best written ones. He's the perfect representation of a controlling moral hypocrite, and the terrifying lengths someone like him will go to blame and punish everyone else but himself in order to clear his conscience.
If you want to argue why you think Valentino doesn't work as a villain, then sure. But, that's usually not the argument I see people making when it comes to this character. It usually seems to boil down to: This character is morally bad, and you're bad and condone what they do if you like them! Not whether they think Valentino serves his intended purpose in the show's narrative well or not.
