Debating Chart Junk
That said, Tufte defends - quite vigorously - a set of views on what he calls "analytical design" that consist in a set of inextricably entangled moral assessments, aesthetic criteria, and empirical claims. And he can come across as, well, moralistic and judgmental. And I find his views generally persuasive!
Of course, Tufte's views are contestable. I recently came across an interesting exchange that assesses his condemnation of what he calls "chart junk" - design features in data graphics devoted to embellishment rather than conveying information. The first installment is this report by a group of computer scientists who conducted an experimental study of Tufte's thesis. The second installment is a defense (entitled "The Chartjunk Debate") by Stephen Few of a Tufte-esque position which you can find here. Few offers a charitable interpretation of what he sees as the flaws in the initial study.
This is an interesting exchange if you like this sort of thing. I know, I know . . . that's a big if!