I think that's perfectly valid. Sometimes a dead guy can make an argument better than I can and it's better to quote him than rephrase it in my own words and pretend I'm insightful. This does however mean that I'm supposed to respond to criticism of the content of the quote since I agree with it.
I agree with it too, and yes it's insightful. I think the key thing missing though is anything more to explain why you feel that way - as you say, you need to respond to criticism of the content of the quote :)
