In reality it probably is true in some cases, and false in others. Some people who are filled with hate may be propelled by this or that into violence; others, with different frames of mind, will be deterred by violence. I'm not aware of any solid research which has ever investigated the balance, and to be honest, I'm not certain how such an empiric investigation might be carried out. Which leaves us with our beliefs: some of us belive one way, others the opposite.
An otherwise standard boilerplate Guardian article following the story of the murder of Vittoria Arrigoni accidentally contradicts the Guardian's dogma:
While many view Hamas as a radical Islamist group, the responsibility of being in power has forced it to sacrifice ideology for a pragmatism that has alienated many of its supporters. Some have rejected Hamas's brand of nationalist Islam and embraced fundamentalist Salafi Islam, which aims to create a single Islamic commonwealth in place of nation states. Tawheed and Jihad means oneness of God and holy war or struggle.To be clear: even according to the Guardian, when radical Palestinian groups begin to accept the reality of Israel's existence, even if only on a very limited basis such as Hamas in Gaza, this inevitably further radicalizes some Palestinians. Put concisely: making peace with Israel will create terrorists.
Mkhamir Abusada, a professor of political science at An-Najah University in Gaza, said such groups began to emerge after Hamas took control of the Gaza Strip in 2007. "Most of the members of the Salafi groups were previously members of Fatah or Hamas. They are dissatisfied with Hamas's failure to fight Israel and Islamise Gaza," he said. "They cannot compete with Hamas but they are a source of annoyance....
The Army of Islam split from the Popular Resistance Committee. It initially carried out operations with Hamas such as the kidnapping of Israeli soldier Gilad Shalit in 2006. When relations between it and Hamas broke down, the Army began kidnapping foreigners, including two people from Fox TV in 2006 and the BBC's Alan Johnston in 2007. Johnston was released unharmed after four months.
This dynamic is not new, and not surprising. Nor should it preclude Israeli attempts to reach accommodation with the Palestinians. It does however mean that even when the accommodation is eventually reached, Israel will need clear borders with the Palestinians, and it will need to control the gates through those borders, so that the murderous Palestinian crazies won't be able to get in along with the peaceful ones. It will not be possible to have an open border running through Jerusalem, of course. It won't. Any division of Jerusalem will inevitably mean a hard border running right through the city. Don't believe anyone who tells you otherwise, no matter how impeccable their credentials.