Complex sentence: His decision to oppose Russian imperialism is also seen as a good one, whereas his detractors have argued that he was a bore who stuck to his ill-thought out conservative principles only out of vanity and a sense on infallibility.
Split into simpler sentences: His decision to oppose Russian imperialism is also seen as a good one. On the other hand, his detractors have argued that he was a bore who stuck to his ill-thought out conservative principles only out of vanity and a sense on infallibility.