To not see that gov't's have responsibilities to keep people in jobs and often deal with dreadful dictatorships in order to do so, is to see the world through the prism of childish idealism.
Take the Saudi's. An elected gov't licensing the export of weapons platforms, made by an internationally recognised company to another legit' Gov, (no matter how much you or I might dislike them) is not a breach of international law. Whereas planting bombs in cars to blow up non combatants, for instance, regardless of how aggrieved you may be at injustices both real and suggested, is definitely illegal in anyone's language.
On the MI5 issue: Its fascinating how when it comes to the govt dealing with appalling regimes, your happy to emote over the morality and the 'injustice' of it all, regardless of what the benefits are. Disgusted by the realpolitik elements. Yet you become so pragmatically cold, hard-headed and factual when it comes to MI5 and Corbyn's links to the PIRA? And it becomes "safe to assume he's innocent of my charge"?
Corbyn approved of, supported and encouraged the PIRA. The evidence is overwhelming, even McDonnell has apologised for his part. Corbyn however continues to lie and obfuscate over it.
Thatcher supported Pinochet, so what? Thatcher and Pinochet are both long dead and gone. The world has moved on. Do you think that bringing up the long departed spectres of the past serves as justification for someone who is still very much alive, very much still in domestic politics and who has, it appears, a penchant for historical revisionism? You cant change the past. If that's all you've got, its very weak indeed.
To summarise Pinochet for all his monstrous actions, wasn't an enemy of Britain, didn't murder British citizens and isn't seeking a mandate to be our next PM. Can't you tell the difference?