Now in paperback, a passionate and edgy defense of free speech in Canada, and the role the internet plays in the issue--from an acclaimed writer and former advisor to Prime Minister Stephen Harper.      On February 28th, 2013, Tom Flanagan, well-known author, University of Calgary professor, and former advisor to Prime Minister Stephen Harper, made comments about the punishment for viewing child pornography that were tweeted from the event he was speaking at and broadcast worldwide. Following the event, in the two-and-a-half hours it took to drive from Lethbridge to his home in Calgary, Flanagan's career and reputation came under siege. Every media outlet made the story front-page news, most of them deriding Flanagan and casting him as a pariah. His university, the Prime Minister's Office, other influential politicians, and much of the media, including the CBC, made him persona non grata before he even had a chance to explain the comments he made.       Persona Non Grata is a superb and convincing defense of free speech--not just in Canada but everywhere--in the age of the Internet, a double-edged sword when it comes to freedom of expression.