Perhaps more ironic than the fact Coca-Cola's Canadian Director of Communications and Public Affairs referred to eating at longtime partner McDonald's as "shameful" is the fact that I disagree.
I don't think eating at McDonald's is "shameful". Heck, I don't even think drinking Coca-Cola is "shameful".
Of course I don't think either are "healthful" behaviours, and would argue that done regularly both could be "harmful", but I wouldn't use the value judgement of "shameful" to describe them.
Examples of what I would consider "shameful" behaviours would include corporate sugar water lobbyists suggesting their products don't contribute to ill health, Coca-Cola executives claiming sugar-water branded dance parties and video games don't prey on youth, and of course Coca-Cola's regular claim that they never target children with their advertising.