There are good and bad people in every community, but there is a civilized way of trying to sort the good from the bad. I have meet many Afghans in Australia, Pukhtoons, Hazaras and even Tajiks that have lived in Pakistan, some of them have lived there for over 30 years. Alot of them love Pakistan and alot of them hate it. I will list down their reasons for hating Pakistan.
1. Discrimination
The treatment when they were in Pakistan was their biggest complaint. Most of the people i meet are born in Pakistan, so they don't know anything about Afghanistan until they get abit older. the discrimination that they faced, the hardships they had to do through just because his parents/grandparents were born in Afghanistan. One guy even said that he didn't realize he was different until he had finished school and wanted to get into Univ. his best friend got into Univ but he couldn't. The difference was that his best friends parents were born in Mardan while his parents were born in Jalalabad.
2. Propaganda / Mis-information
Alot of Afghans hate Pakistan because they think that Pakistan took over their land. The Propaganda against Pakistan is very strong and it is influencing how the Afghans view Pakistan. They are told that while they were fighting the soviets, Pakistan's ISI was busy finding building that were in good shape and they would blow those buildings. They are also told that the only reason Pakistan took the Afghan refugees was so that Pakistan can exploit their plight and collect and keep all the donations that were meant to help the Afghans. One guy even told me that it was the Indians that came to help the Afghans to fight the soviets and that the Indians are the only ones helping them rebuild their country.
3. Taliban
Another reason that Afghans hate Pakistan is because of Taliban. The stories i hear about how ruthless these guys were is pretty scary. Now i am not sure if all them are true, but i have seen videos which are similar to what these guys have told me.
So you see in part some of their hatred towards Pakistan is justified, but the hatred has been elongated by the propagandist and India who want to use it to create problems for Pakistan.