I believe that CCD has multiple causes and dimensions. Bees are very specifically evolved, and much like any overtrained system, have weaknesses. A population of bees is always under stress - varrora destructor (a terrible kind of bee mite), various bacterial, viral, and fungal infections, other bees, predatory insects/animals, and more. Bees constantly fight to overcome these threats.
Now, with the introduction and high usage of pesticides/herbicides, we've pushed them over the edge. More so than glyphosate (RoundUp), I think neonicotinoids are the most dangerous chemical. Active in low PPM, long lasting (decade+), and just dangerous enough to bees to make a CCD incident possible.
Bees' direction finding is really incredible - imagine driving hundreds of miles away to a building with only the angle of the sun and a heading to work with. Neonicotinoids make bees "drunk" for lack of a better term - they cannot find their way back home. Only the oldest bees go out to forage. That way, if they get lost or sick, they're more likely to die and they've already achieved much of what the hive needs of them. If less foragers return, you have less food for the hive, so less new bees are made. Over time, as the bee population ages, you're left with less and less foragers, less and less bees, until you open your hive one day and find a handful of dead bees, a dead queen, and starved larvae. This is a classic depiction of CCD.
As for the ethical treatment of bees - as insects, I don't believe they have an ethical or moral component. They are put under great stress every year to pollinate almonds - it is the greatest bee mixer/spring break in the world. It is also how we get all the bee diseases/pests spread quickly. I'm more concerned about the treatment and sales of honey. Supermarket honey is very suspect - overcooked, mixed, strained to remove any "impurities". Sometimes it isn't even real honey or has been relabelled to be local when it isn't.