This is beautifully said 
This is simply me speaking respectfully from my own, slightly different path, but I’d personally consider self-defense spells such as Return to Senders or Freezer Spells to fall into the Gray Magick category. Not “light” but not “dark/baneful”, either.
Then again, just as you’ve said, one spell could fall on a different part of the light/dark spectrum than someone else’s spell of the exact same type. At the end of the day, magick is a tool we wield - I believe that ethics are found in the intention of the caster 
I second Tracy’s idea of using knot magick - it’s great for binding, be it energy or actions. There’s a freezer spell on the site specifically for stopping lies and gossip. Here it is:
A note that it’s not designed to target a specific person, but rather any lies and harmful gossip directed your way. It could, however, like all spells, be adapted to suit a particular situation.
If you’re short on ingredients, the Spells8 Virtual Altar has everything you’d need for this spell. You might consider casting it there! You could take a screenshot of the finished jar and save it on your computer to store it for as long as you need to 
This is interesting to hear! I’m very biased about it, but for me, thinking divination is baneful would be along the same lines as saying it’s “evil” to check the weather forecast. There are plenty of folks using divination for self-improvement, healing, and other types of magick generally sorted into the “light/white magick” category. I guess it just boils down to different perceptions based on their different experiences, I suppose.
I’ve been working through some beliefs lately that examine the nature of “light” and “dark”, how they manifest in the universe, and how I define them in my own practice. This space is educational and appreciated! It’s helpful to hear everyone’s experiences and beliefs. Thank you for opening it up, @SilverBear