I think that is a profound difference of opinion about what is and what is not metal (a debate that never seems to die). I think slow brooding songs or even songs with acoustic guitar can be as metal or even more metal than those that just feature stereotypical heavily distorted guitars and screaming vocals. In fact I would call most of Rob's post Stained Class vocals more cock rock than metal but to each his own.
Yeah, the very nature of musical sub genre is subjective so trying to fix any hard fast rules to what is and what is not metal is kind of like herding cats. By debate I really don't mean anything negative. I just mean a discussion with two different opinions. They tend to be a little more revealing than those where everyone agrees on every point but every time I mention metal it reminds me of the years I spent arguing with people about whether Motley Crue or Skid Row were metal. Decades later the debate is finally somewhat settled but I remember a lot of folks turning away from metal because they were tired of being asked about the latest exploits of Twisted Sister or whatever. It seems now a lot of young people are calling Sabbath Proto Metal and to me that is at least as rediculous as calling Warrant or Cindarella metal.It wasn't really a debate I was trying to get in on, I was more going by what something sounded to me. I understand both sides of the argument though about the album. I respect whoever calls it metal or hard rock. I think it can be seen either way. I agree with you regarding slow brooding songs. I think metal is something that will always be heavily debated in terms of the sound but Ill also add I think metal songs tend to have a bit more of a complexity to them than the usual hard rock material which tends to be I guess more simplistic and straightforward. I get a bit of each on Sabotage.
Some songs are absolutely simplistic and yet have changes or structural anomalies that are...well....metal. Others, like Megalomania or The Writ are just metal through and through to me. In fact, a lot of times when someone asks me what I really think the defining metal sound is I go for a song from this album.
Not trying to be argumentative here. I just enjoy examining this stuff.