Haha someone could write a book on that topic. I will just jot few of the reason.
He is responsible for more than 10000 deaths in a peaceful country.
He is responsible for deaths of many intellectual people apart from other innocent civilians and uniformed citizens.
He is responsible for bringing arms to the society, where every teen has a very easy access to the arms.
He is responsible for the increased crimes.
He has acquired properties of hard working citizens through fear and intimidation.
He has lied to the nation by giving two different speeches, just like Prachanda.
He is responsible for the lost of trust in democracy. He actually shares this blame with other parties too.
He is communist.
He shares the responsibility for the political deadlock.
He took away daura suruwal.
He does not have any respect for the martyrs. He broke off the tradition of going to sahid gate.
He does not have the respect for the founder of nation Prithvi Narayan Shah.
And list goes on and on. In one word he is a "TERRORIST" thats why.