Michael Collins was assassinated because he had reneged on what his organisation (the Irish Republican Brotherhood) stood for, according to the party of his assassins. The idea of a Republic, with all power derived from the will of the people, without a monarch even as titular head of state granting power from the top down, was important -- an example of an abstract notion having real and concrete effects.
The IRB was a small secret society dedicated to armed insurrection operating within the wider framework of Irish nationalism. It was respected and at the same time feared by many other groups and societies working towards similar goals in Ireland a the time. Operationally speaking, it was a revenge killing and a very important blow struck against the Treatyite party in the Civil War that was then raging in Ireland. Eliminating Michael Collins meant that the IRB (a fundamentally undemocratic group) ceased to be the huge threat to other groups that it was while he lived.
WRT Climategate -- yes there was overstatement of the case, but that is not to say that the Bush administration had it right and there is no such thing as global warming. Certain facts about our impact on the planet and its atmosphere remain and must be recognised and dealt with.
The Marxists I have known believe every word of what they preach; their belief seems to me to be almost religious in nature. They tend to be humans, and get their beliefs about their individual communities, as well as their motivation whether pro patria or pro Marx from the same place that anyone else gets theirs from -- you can't argue that it was only the Soviet citizens in WW2 who, having been indoctrinated into Marxism, were then fed a handy patriotic lie in order to get them to fight for Marxist world domination, while in every other 'nation' no such cynicism ever existed on the part of the ruling classes, and the citizens felt some natural upsurge of their innate patriotism. Either all humans are capable of being manipulated by a carefully crafted patriotic narrative or none are.
'Marxists seek to rob and deny other countries of their patriotism, in order to weaken them, but they are patriotic for their own country in order to strengthen it.'
You could substitute any other proper noun here for 'Marxists' and it would hold true -- Nazis, Chinese, Indians, Pakistanis, Americans, Russians, Vikings, North Koreans, Iranians, British Imperialists, Spanish conquistadors, Afrikaaners. Whether they are 'patriotic' in order to strengthen or fearful of the consequences of weakness is debatable.
I was brought up as a Catholic and maybe it's what you could call a 'sturdy indefensible' aspect of how I go through my life. It's certainly not scientific or logical. I was happy to accept what I was told and taught about my religion; others in my family did not and do not. If I had been born Jewish I might keep kosher and worry about eating anything my sister cooked in her kitchen. (I may have made up for my quiescence in this regard by an excess of contrariness in other areas...) I am the oldest child, maybe that has something to do with it... I can see in patriotism something of the same dynamic and suspect the same capacity to manipulate opinion may be in effect. Religious or ritualistic practice in its most rudimentary form predates any evidence of patriotism though. I don't think the two can be placed on the same level (thinking of the Syllabus of Errors of 1864 and what it had to say about nationalism, which had only in the late 19th century come under the papal radar.)