The point is that a corporation "accepting" Bitcoin is not an endorsement by the corporation for Bitcoin. And even if it were, corporations are hardly the pinnacles of ethics and legality.
And by the logic you guys are espousing, then e-commerces don't accept any currency that isn't the one their government forces them to use either, because they do it through intermediaries like Visa.
I don't buy that either. The only thing it is an evidence of is that said corporations want to attract customers of a specific demographic. Overstock.com CEO himself is a libertarian, for example. If it wasn't for him I strongly doubt they would have implemented Bitcoin payments on their site.
I mean, if Bitcoin is so useful, why have sites that have implemented it have done a miniscule if not virtually negligible amount of sales through it?