Each tier has trolls. You hit trolls from bronze to challenger. The difference in trolls in different tiers is usually skill / knowledge level.
So bronze may have less trolls (people intentionally being bad) because bronze is the bottom of the totem and you have a lot of people who are either relatively new, have less game knowledge, etc. As you move up it is assumed that you have more game knowledge. Though some people have really good game knowledge but just don't have the skills/mechanics to advance or can't make the in game decisions, although they can easily find the correct decisions when they review the game.
Actually, when I was in silver what I found annoying was the amount of people that would do 1 of 2 things :
- hate on players that were bronze (having a tier elitist idea is annoying)
- players that wanted to get into gold so bad that they would rage/complain/etc at the drop of a hat.
Although it is worth noting that #1 happened a lot more than the rage. Ranked really is not as bad as people say. The bad games just tend to stick with your memory.