These reasons are absolute bullshit.

First of all, "trip hop" is such a broad term that it can only clearly describe the scene artists are part of and not the specific sound of music. Otherwise, how can both Massive Attack's "Angel" (an aggressive, dub-influenced alternative rock song) be considered to be in the same genre as "Protection" (an electronic R&B/pop ballad). How can Portishead's experimental, almost entirely non-electronic, guitar based, 1970s style krautrock/psychedelic folk album Third, be considered as part of the same genre as the pop oriented electronic slow jams of Sneaker Pimps? They can't. They are both trip hop, but that's because trip hop is a description of a music scene (if an artist is widely seen as trip hop, they are trip hop), not a musicological term.

"Alternative rock" is almost as arbitrary, but it does have one common factor, making it (unlike simply "alternative") a clearly defined genre. "Alternative rock" is primarily based on the guitar, bass, drums instrumentation of rock, to which other elements may be added, and the primary musical basis is rooted in punk or post-punk music. Kid A era Radiohead is right on the edge of "alternative rock," but half the songs on that album are still centered on that instrumentation, the band's influences include post-punk, and the band's live performances (even of songs like The National Anthem that were not exactly rock in the recorded version) generally use a rock style. Also, Kid A fits more closely with rock than with hip hop or pop, even though it draws elements of their production style. Therefore, even Kid A is arguably "alternative rock."

Let's compare this to Plastic Beach, the most recent Gorillaz album. Guitar/bass/drums are present on the album- usually in sampled form. This is similar to how rock instruments are used on, say, To Pimp a Butterfly and My Beautiful Dark Twisted Fantasy, or even Beyonce, Rihanna and Carly Rae Jepsen's recent pop music.

The aesthetic of Gorillaz, like these artists, is created by sampling the performances. Also, guitar instrumentation may be present in Gorillaz at times, but it is very rarely the main instrumentation. They primarily use synthetic instrumentation, or they may sample guitars to the point that the results don't sound like rock music. In this way, Gorillaz are similar to most hip hop and pop artists (actually, Kendrick is arguably more of an alternative rock artist, he really emphasizes guitar/bass/drums, drawing from funk and jazz fusion as well as rock).

Outside the UK, Gorillaz have experienced massive success, far outweighing Damon Albarn's former band's status as a "one-hit wonder" in America. Unlike Blur, who failed to "break America," Gorillaz easily got their songs into radio playlists, and were rewarded with Grammy nominations in the top categories, like Song/Record of the Year.

Unlike LCD Soundsystem, Strokes and other major-label but culturally-"indie" acts, Gorillaz experienced mainstream popularity as a result of their pop radio play and their non-rock-based sound. Gorillaz's total sales dwarf even Arcade Fire, and their radio play dwarfs Radiohead. They are actually huge in America and everywhere else.