Barry Rubin carefully read Tariq Ramadan's op-ed about how benign the Muslim Brotherhood is (I wrote about this yesterday here), and says it's full of lies. Given Ramadan's intellectual stature, there's no chance he didn't know this.
Unless you can be intelligent, extremely well educated and an important public intellectual, and still not know when you're blatantly lying. Sadly, history teaches you actually can. Easily.