I think you should use the theme you like without caring about what anybody else says. Besides, since you didn't know about it before you installed it you did nothing wrong.

Regarding people who complain about it: they are walking contradictions. They rely so much on branding that even when the quality of the content is good they feel betrayed (see Drew's comment above). Yet that brand is supposed to convey quality of content. When the get the quality without the brand they complain! As if no quality should be allowed to exist outside of the Svbtle network!

I think that what Svbtle tries to do is noble and appealing, hence their apparent arrogance and the bevy of defenders we see. I also think that the creators were trying to solve a genuine problem: when anybody and everybody has a blog, a voice, and can say anything, you need a way to filter out the noise and separate the wheat from the chaff. I think the idea that to have a design that signifies quality is the first (and sometimes the only) solution a designer would think of.

Yet, regardless of their high intentions, the reason so many duplicates, knock-offs, adaptations and inspirations exist is not because of the design (which is nice and well done, but not to the extent or speed with which it has proliferated) but because of their attitude and desire for exclusivity. The psychology is the same as behind Anonymous trolling, behind internet piracy, behind any teen rebel: oh you say I can't do something, well then BAM I'm doing it.

The tragedy is that the brand has overtaken the actual design so much that it is no longer allowed to exist by itself. When someone (such as you) comes across it, likes it, and wants to use it, purely for the aesthetic appreciation of the design, they are vilified and antagonized and blamed for trying to steal the brand. The brand is a monster which has consumed all that was once good in this design.

Good ideas will be copied. If you don't want something copied, don't share it with anyone and take it to the grave. People will copy things if they can, especially when it is something as simple as a web page design, and especially if you ask them not to. This is how the web grows. This is the nature of things. All else is whining.