Okay, first let me start off by saying that not liking something =\= being close-minded.
I'm not about to say DC is or isn't close-minded, because frankly close-minded is the race card of musical discussion and typically has no place in the discussion 90% of the time. DC, I'm sure there is a musical technique out there you don't like, and that's okay, it doesn't make you close-minded just as generally not liking growls doesn't make me or anyone else close-minded in and of itself. If you shut yourself off from something without any real reason that's another matter completely, but I think most people here who don't like growls have given them substantial chances and have been exposed to some variety. I even had a growling round in my roulette.
I can't tell you how many times certain bands I love have been ridiculed over the years, but it just comes down to people not liking it. Most of the time this doesn't mean they are at all close-minded. In the same way I generally dislike growls, and often I do find them laughable, but it's simply a matter of taste, and on the same token that the entire internet can go lolNickelback people have to accept that some people are going to go lolGrowls and lolHighPitchedVocals and just accept that not everyone is going to like everything.