I played a kender for close to 2 years... played him as written, and it was not a problem.
He stole all sorts of things from PCs, and he thought locks were purposely put in place only to 'challenge' folks. I used to 'find' all sorts of things, including gems and money. OTOH, Kender also don't care about *their* ownership either. Once we got to town, if someone was 'missing' their collection of matching rubies, they could just ask the Kender for some gems. He had a neat set of matching rubies, and even a nice emerald to go with it.
But a player, any player, playing any PC, needs to pick and choose when they play up their personality. Enmity towards a race, cowardice, avarice, chaotic tendencies, lawful tendencies, etc etc can all be problematic if the *player* allows them to be problematic.
So sure, the Kender may have found money, and may have even found a really shiny sword. But you find the sword in the morning as folks are getting ready, not in the dungeon as folks are entering the final room. Just like the fighter that *hates* elves expresses that hate in an appriopriate manner for the game, and doesn't just kill every elf he sees.
The vast majority of things we do, or don't do, in real life is because of what we have learned...what we know. It has very little to do with "fear". If I am standing on the roof of my house, the reason I don't jump off isn't because of 'fear', its because I know it can lead to a lot of physical pain and injury. A Kender would operate the same way. He is no more or less afraid then I am, but also isn't any more ignorant of the consequences.
The only difference is that if the house was on fire, and I had to jump, I would hesitate because of fear... and he would just jump, because he knows he has to.
I am sorry for you that have had such a bad time with Players abusing kenders, just like I am sorry for those of you that have had such a bad time with players abusing Paladins, or thieves, or Chaotic PCs, or PCs with stupid backstories, or ones that would run away, or whatever else the *player* decided to do.