Do you mean, why is the term applied to the bad SEO methods? OR why are the bad SEO methods thought of as bad?
"Black Hat" techniques are unethical methods that some Web site owners use to get their site listed on search engines. Here's a list of four common techniques. Those are Keyword stuffing, Invisible text, Doorway pages, cloaking etc.
That doesn't answer her question about why they are perceived as negative. I didn't quite understand the question but I'm pretty certain she wasn't looking for a list of methods.
because black hat technique provide different content for google and for user. google allow only site which is useful for user there for black hat technique as know as negative.
Black Hat Seo are illegal techniques used to "game" google for better rankings ect.. over time its not going to work as google will catch on and your site will be penalized perhaps your website will be wiped out for good..Build your site the right way with good quality content. In the long run you will be better off for it.. Hope this helps..
As Low quality content, Keyword stuffing, invisible text, Mirror links, Article spinning, duplicate content and many more are black hat SEO techniques. @Tejasi , These all are shortcuts to target the Search engines but Search engines became more sharp and intelligent now, and rely on audience. "Just Do work for audience, Search engines automatically 'll work for you."
Blackhat SEO is used to rank your site in Short time. So, When you get caught by Google, your ranking will suddenly dropped and you will get manual penalty in your webmasters tools account.
Blackhat SEO goes against rules of the game. In that sense, it is normal that people will not like it (especially those who are doing legit work and you are draining their profit by doing unfair things.