This something I'd had to get my head around as before MC modding community the only Mod community I had gotten in was Nexus and those folks have little to no issues with mods modding mods combining mods ...or any of theat as long as their credited. So the whole idea of a mod author geting upset becuase someone used there mod in a pack was alien to me.
That said I can see the whole respect angle and really only becuse no one wins if the community piss off a mod developer and they stop modding.
The thing is that Minecraft doesn't have a site like Nexus.
Nexus is a great central location for mods, on the games they support.
And it makes it a good way to have a lot of visibility for all mods, and modpacks can easily throw a link to the included mods.
Minecraft doesn't even have a "search by categories", and it is a pain to look for a od that you don't remember the name off.
Added to this is the fact that some rules of MC forums made many mods create their own site/forums, splitting the content all over the place.
If you add the fact that, back in the days, the mods where a pain to install, conflicts very hard to handle, and updating a single mod would take hours, because you would have to reinstall everything from scratch.
If you see it that way, you can understand why people would not want to spend hours to search for mods, install them, make countless edits to the various config files to work out the ID conflicts, and so on.
Don't misunderstand me, I am not defending the ones that disrespect the authors' wishes, but I can understand why the people jumped on an easy way to play with a lot of good mods, without having to worry about forge version, or ID conflicts.
I was personally of those that preferred to take hours to custom-tailor my game, but it is a work that many people are not willing to do for a game, especially when an alternative exists.
I mean, I even play with FTB now, because it's so much easier to just click and play, and have nearly the same mods anyway. Plus I can add those I want.
Anyway, when a person chooses a product (here, a pack), they tend to only see the good parts about it, and to defend it to great extend, that is just how we all work. It doesn't mean we are right or wrong, nor does it mean that anyone is right in the end, so it can start great deal of frustration on both sides, leading to a conflict (word based, but conflict anyway).
*Arg, again a long post with no content...*