The Altnaveigh massacre happened in 1922. That's Altnaveigh, Northern Ireland, 1922. Look up your history.
Stop making it about yourself, so.
You know there were some people born and brought up in England in the IRA, too?
If you've read the book "Killing Rage" by Eamon Collins, you'll be familiar with "Mickey", aka Michael Collins, who was the Newry IRA's top sharpshooter in the 1980s. He was born and brought up in Manchester.
James Connolly was brought up in Scotland.
The country of origin of the attackers is irrelevant. The nature of the attack is relevant. It was against a British soldier, like so many other IRA attacks. Therefore it's of an obviously different nature to the Manchester bomb or the London attack.
You mention the word "war". "War", ie. the "War on Terror", is the preferred terminology of the west. Not to mention the wars in Iraq, Afghanistan, Syria and Libya. And that immediately grants a legitimacy to ISIS, Al Qaeda or whoever.
It's not me that is granting that legitimacy. It's the governments of the USA and the UK that are doing so.