I think that terrorism involves attacks deliberately aimed against civilians, because civilians are helpless and can't fight back.
So if you're a terrorist, you typically don't want to fight opposing soldiers, since they can shoot back. Instead, you want to go after the softer vulnerable parts of society, to terrorize them.
Regarding the original poster's comments about different religions and terrorism, I assume that because he is a Muslim, he feels that other religions need to be blamed more. Well, the Tamil Tigers are not a religious terrorist group - Tamil is a linguistic group (people who speak the Tamil language), and there are Tamil speakers who are Hindus, Christians and Muslims who actually belong to the Tamil Tiger terrorist group. Likewise, the IRA (Irish Republican Army) is a terrorist group composed of Irish Catholics, but not all Catholics, nor all Irish. The FLQ (Front de Liberation du Quebec) committed terrorist acts during the 1970s, and was composed of French-Canadians in Quebec who were fighting to create an independent country. They were not composed of all Quebecers, nor all French-Canadians, nor were they fighting for the Catholic religion even though many French-Canadians are Catholics.
The degree of correlation between a terrorist group and a wider religion would probably be proportional to the level of feelings in the wider religion towards the cause that the terrorists are fighting for. For instance, not everybody in the West supports Israel against the Palestinians - there are many people in the West who support the Palestinians over Israel. But how many in the Muslim world support a different ethnic/religious group over their own? That to me is an important question, which affects credibility and objectivity. If you only support your own group all the time, regardless of the circumstances or the situation, and cannot provide any examples to the contrary, then you're pretty much advertising what your biases are and what your credibility is.