^Of course what Kira did was terrorism, and she freely admitted it on many occasions. Terrorism doesn't just mean "something the evil enemy does." It's a term that has a specific, objective definition, regardless of how pundits and politicians abuse it as a term of emotional rhetoric. Terrorism is is the use of random or excessive violence to induce fear and despair in a population in order to pressure them into abandoning an occupation, war, or other policy. It's generally a tactic used by a weaker group against a more powerful group that can't be defeated by force alone and thus must be demoralized to the point that its own leaders or populace decide to cut their losses and retreat. Which is exactly what happened in the Cardassian Occupation of Bajor.
In Khan's case, he used the tactics of terrorism for goals that were not actually terroristic. He bombed the archive in London, not to terrorize the populace, but to destroy the secret Section 31 facility it contained, and to lure the Starfleet leadership to a specific place so he could strike at them. Terrorism was just the cover he used, the feint that disguised his true intentions. This is something we've seen done in many movies, such as Die Hard.
I'm not disputing that there's an objective definition of terrorism. Yes there is. But we all know in reality that one man's terrorist is another man's freedom fighter. And in reality all we have are subjective interpretations of events when those events are not hard science experiments. No one has the all-seeing eye of God to have a completely objective view of events.
I'm only saying that the Bajoran government did not throw Kira into prison because they did not consider Kira's actions as terroristic. Or if they did, they pardoned it because it was in their just cause of freedom.
And Starfleet and the Federation do consider bombing their archives and killing people as acts of terrorism. I'll concede that we may interpret Khan's acts as non-terroristic but clearly militant, since we know his ultimate aims.