Oh, I'm not saying it was bad that he killed Blofeld. I'd have done so in a heartbeat. I and others in the fandom have just pointed out what's seen as hypocrisy, legitimate observation or not. Bond's wife was murdered by the man who was about to murder him with a remotely controlled helicopter. Frankly nobody is going to handcuff Blofeld and have him arrested and arraigned if they can dump him down an industrial smokestack. 
