I only play in Open because it adds risk and a even a little fear for me. I play a lot of tough survival games, and enjoy titles like DayZ and Dark Souls. I grew up playing Ultima Online in the 90's, and that game is still to this day the most hardcore game I've played (until Trammel came out). People were almost encouraged to grief and cause problems for other players...The solution to it not ruining your game was to get better and learn to avoid the mistakes and traps that the griefers would set.
Also, there isn't an AI in existence (yet) that can outsmart you. No matter the difficulty, it is only a matter of time until a skilled player is beating any and all computer opponents close to 100% of the time. The point is that games quickly become boring when there is no real challenge.
Another point, is there is very little actual griefing that occurs here. I have been playing open mode only for 3 months, been to Sol, a few engineers, and some other high traffic areas, and I have never been attacked by a player. There is an event coming up this weekend (if you haven't heard), and the stations nearby aren't even in lockdown. It seems like every one is on their individual quest to make credits and upgrade their ships, and only incidentally run into other CMDRS. I definitely don't feel like the community is toxic or that you have to constantly watch your six while flying around in open mode.
Lastly, this is a simulation game. Show me a real life scenario where there are no bad guys, no competition, or no one willing to bend or break the rules to get ahead quicker, and I will show you someone who is very naive. I want to experience a simulation for a living, breathing, galaxy. For that, you need actual real people.