Beware: long post ahead...
I could be wrong, but perhaps some people are irriated by people assembling commercially available loops and calling themselves songwriters. I would tend to agree with that, however, in that situation, isn't it painfully obvious to the listener? It usually doesn't sound like a good song, unless maybe you are into EDM. I hear people play back a little musical motif which they generated using their iPhone, and say they wrote that. I've got news for them, they won't be able to retire on that.
How about this: if someone uses a very small bit of a commercially available loop, which no one would recognize as being a loop, and then assembles the loop material into a song which blows you away, does it mean that they are not a legit song writing?
What about people who use BIAB - they enter the chords, and BIAB poops out an arrangement. If it sounds great, and you like the song, then what?
Audio / MIDI loops, BIAB, samples can all be sources of inspiration or place holders until the song is completed.
If John Lennon relied on loops or BIAB to help him write "A Day In The Life", why would I care?
Doesn't the songwriter, assembler, or whatever you want to call them get any credit for determining what sounds good?
Even a songwriter, whose brain, muse or whatever is generating chords, melodies, and rhythms has to pick and choose what sounds good and what doesn't.
It all comes down to what the completed song sounds like and how it is embraced by the listener.
We must also differentiate between sounds, production and the very kernel of the song. Depending on the genre, a great song could be performed on a guitar, piano, voice, or a combination of these. Most of the great songs stand up to this naked test. Of course, genre comes into play. I like progressive, electric jazz and funk. Others are into EDM and all the variations of Urban music. I guess maybe the naked test doesn't always apply.
About 25 years ago, I was in a music store, and a dude was playing with a Yamaha 4 operater FM synth with a built-in drum machine. He created something so incredible, I really had to re-examine my constant need for the best sounds and software to come up with tunes.
But don't get me wrong, if it weren't for the technology we have, it would certainly be much more difficult for me to come up with tunes. I don't play keys, drums, sax, etc. The sound of these instruments and how they are approached so differently than guitar really makes a difference to me.
Some people can write a hit on a tape recorder, some use Garage Band and loops, and others use the creative features and tools of the wonderful technology available to us to give us a nudge - it's all fair game.
Some people need a rhythm to get them going. Some need chord changes, melody, or a lyric or title. Some people dig synth sounds - case in point - Joe Zawinul - RIP, said he was often inspired by a synth patch.
Different strokes. Different folks need different levels of technology to compose music.