This is up for debate and goes toward methods rather than ideology. the Empire is well known for using oppression of all species (like the oppression of Toprawa) but was the established order. The Rebellion did destroy several major works made by the government (such as the Death Stars) and these did have a terrible toll on both the economy and political structure of the Empire.
As such, it would depend on which side you stand on. Yes the Rebellion was fighting against military installations but the Second Death Star wad filled with contractors making it and thus the blood of millions of innocent lives are on their hands. The Empire is also not faultless but still has done bad.
In the end, I'd say that both sides are terrorists.
Depends if you are a Republican or an Imperialist
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