Illicit language towards the living and the dead
Q: What is the hukum for speaking negatively or using vulgur words against a dead person, muslim or non muslim?
A: It should be avoided. The Messenger of Allah said, “Mention what is good about your dead, and refrain from speaking about their evil.”
Al-Tirmidhi, 1019
Also, using vulgar words is prohibited in general. The Prophet ﷺ said, “The believer is not a taunter, curser, obscene or indecent.”
Al-Tirmidhi, 1977
However, some people committed crimes and injustices publicly before they died and it may be necessary to mention those acts.