Actually, they too can create a PG with PvP rules...
I heard that this actually happens for some PvP players, but it may just have been a rumour.
For pitched battles among pre-vetted participants, this is what some do. PvP League took place in a private group.
But Private Group is a poor substitute for Open when the goal is to experience whatever, and whoever, may be out there, regardless of whether one is specifically looking for PvP or not.
Come over to solo with me, it’s a bit lonely sometimes but I’ve been playing for years and I’ve not met a single idiot yet...
Except for each and every one of the NPCs.
Ultimately, that's why I only play in Open...because the NPCs are not convincing placeholders for people. They aren't even particularly good as NPCs go. They only exist when a CMDR is there to spawn them and they can't actually do anything to the setting themselves.
Rather than complain here, try negotiating with the person(s) that block you. However, be prepared, one doesn't always win a negotiation.
You are making two assumptions that are frequently not true:
1. The person blocked is the only one negatively affected.
2. That any knows who was doing the blocking, or even if the presence of a block can be confirmed to any degree of certainty without exhaustive process of elimination.
(I don't particularly have an agenda (as such) apart from everyone should be able to play the game exactly as they wish - in the game as it is today this is impossible)
That goal is fundamentally incompatible with any multiplayer experience, because there are as many different ideals as there are players. Not everything can be optional, and not everyone can be allowed to dictate their own terms to everyone else.
What you want is only viable with an offline single-player game.
Blocking doesn’t prevent the ganker from playing their own game does it?
It certainly interferes, and not for just gankers (or whoever the target of the block is in any given example). Indeed, anything that degrades instancing prevents some portion of the encounters with other people that are ostensibly the entire purpose of trying to play in Open. Some degree of this is inevitable, due to technical realities, but these are problems to be overcome.
I suppose to what extent of 'prevent' is required for your threshold. If it has to be absolute, then no, there is no practical extent to which blocking could be used to completely stop someone from playing. However, any behavior I've see cited as a rationale to use block is equally incapable of preventing someone from playing.
Someone who blocks too much will likely just end effectively consigning themselves to solo and therefore not a factor. They will just find themselves shuttled into their own instances.
The more one walls one's self off, the more overt the problems for anyone who does manage to find themselves instanced with that CMDR.
A few blocks here and there are very hard to notice or prove the existence of. However, even in the case of mass blocking there will always be those someone hasn't blocked. If the local population is low enough, or the positive factors for instancing good enough, I could easily find my CMDR stuck in another's self-imposed ghost town against my will, with little recourse but to try to identify the source of the instancing troubles and conterblock the offender (which might make me responsible for the same sort of trouble for someone else, which is a level of hypocrisy I am not capable of) or to have my CMDR vacate the area, for no contextual reason.