I'm all for freedom of speech, its guaranteed under the Constitution of this great country. So I would suspect that flag burning would be a exersize in freedom of speech,... maybe.
However, nearly all of you have missed one large symbol of this flag except for Ken's last post (and Al's post too). The millions of veterans who paid the ultimate sacrifice defending this country.
I find it ironic that this person thinks things are grevious enough to burn our flag. For nearly 200 years Canada and the US have shared the longest undefended border in the world. Canadian and US military personnel have fought and died side by side several times (and I would expect that this mutual defense will continue for many years to come). So while this person is Canadian and doesn't like some policies being carried out at the moment, he finds it acceptable to dishonor both American and Canadian veterans (as well as UK, Australian, and other British Commonwealth veterans) who have repeatedly allied for mutual defense.
My only response to this person would be to flatly state, "How many of your relatives returned home safely from conflict because of the sacrifice of Americans". There is a real possiblity that this person wouldn't even be here today, if it weren't for the courage and bravery of an American.