You’re paying for SP, the fun in a sandbox is up to you to create or not as your playstyle dictates.
It is not harrasment purely because you dislike his reason for deccing you. What is harrasment is clearly stated in the EULA and specifically (at the time) allowes him to roleplay that the belt is his and dec you for it. I’m not going to argue about the soundness of their reasoning but you’re playing a game all about fighting over resources so that particular reason is fine and supported.
Secondly, it is not harrassment purely because 97% of the wars ended in no combat. Your choice not to fight does not make anything harrassment as stated above.
You answered your own question, you could not be in a player corp if you don’t want to PvP. It’s easy to call any contradictory information “blah blah” but that’s not a reasonable way to argue a point, if you have one. You had every choice to avoid decs by not starting your own corp and declaring yourself fit to defend yourself.
Here are some examples of why this is a stupid argument :
Moving your pawn 5 squares forward in chess because why should I not be allowed to play CHESS the way I like?
Taking the pot in poker with a single 3 because why should I not be allowed to play POKER the way I like
Being able to legally shoot everyone in hisec and lowsec because why should I not be allowed to play EVE the way I like?
Be in the NPC corp and tank your ships while being smart about how much you put in them. Both problems solved, enjoy your happy industrial life.
CCP want to offset the goodness of having your own corp with some risks, like EVERYTHING ELSE in EvE. You accept risk in exchange for opportunity. My main issue with your narative is that you haven’t explained what’s so impossible about being in the NPC corp and sharing a player created chat with other players so you can still chill together and do stuff as a group.
You can use one of the hundreds of public facilities, owned by people who have grown their group enough to defend it. Sounds pretty reasonable to me.
Isn’t it strange how back when the game was dangerous and had few rules loads more people wanted to play? Isn’t it interesting how every change CCP have ever made to satisfy the crying of industrialists has screwed the game a bit more and lost all those players?
Correct. But an MMO designed specifically from the ground up as a PVP MMO does infer at least a small amount of exposure to PvP. As I’ve explained it’s really easy to avoid the PvP to a great extent by flying carefully.
Can you list some of these changes please? If you look at the data you’ll notice it’s actually anti-PvP changes 
Crimewatch and the removal of the watchlist to name a couple. There was also that study that proved players exposed to PvP early were more likely to stick with the game so… there’s some data too. Where’s your data?
To close, wardecs are screwed. I’m not pretending the way things are is optimal, but the worst thing CCP could do is allow people to have the full opportunity in Hisec with none of the risk. The risk is currently too high, but reducing max active decs to 1 - 3 per corp / alliance would eliminate the problems you have without destroying the game. You would still have targeted wardecs happening for territory / structure bashing / score settling but you wouldn’t have the blanket dec situation where every indy corp is decced 3 weeks of every month. Decs would happen only if they were really worth the slot.
Your OP was awful tho, your reasoning is poor and you seem to have little grasp of what makes EvE tick in the first place. You want everything in the game available to a rank solo amateur at 0 risk because otherwise you feel discriminated against and that’s ridiculous.