"Even if there is a war you cannot kill just anybody," he said
Mr Aamer, 48, returned to Britain in October after being held without charge for 13 years at the US military facility in Cuba.
During his time in captivity, Mr Aamer's lawyers said he was tortured and held in solitary confinement for 360 days.
In an interview with The Mail on Sunday, the father of four spoke out against extremists: "How can you give yourself the right to be living here in this country, and living with the people and acting like you are a normal person, and then you just walk in the street and try to kill people?"
He said Islam did not allow the killing of civilians: "Even if there is a war you cannot kill just anybody, you cannot kill kids, you cannot kill chaplains, you cannot just go in the street and get a knife and start stabbing people.
"If you are that angry about this country, you can get the hell out."
On the rift between Muslim and non-Muslims, he said: "It helps their (extremists) cause... if you keep looking at people like they are terrorists before they do anything, then you will push them towards violence."
Mr Aamer also said his period of detention will stay with him forever, even though his reunion with his family reunion "washed away the pain of 14 years".
"It's always going to be in the back there in my mind, it's going to be sitting there, coming back from time to time," he said.
"It's a long period of experience and it can't be just gone."
Mr Aamer was originally detained in Afghanistan in 2001, accused of having links to al Qaeda. He was described in US military files as a "close associate of Osama bin Laden" who fought in the battle of Tora Bora.
However, Mr Aamer says he was doing charity work and in 2007 the allegations against him were dropped.
Mr Aamer is now expected to bring legal proceedings against the UK government over its alleged complicity in his mistreatment.