1. They can't afford bitcoin.
2. Too late to the trend, they are jelous of peoples who get into the trend long before them so that those peoples earn more than them.
3. They want to make peoples leave bitcoin and chose other digital currency which they have bought with the intention to raise its value, greed are disgusting when are too much that you do anything to get what you want.
4. Etc you can think of.
So don't mind those peoples, only sell your bitcoin or buy it when you see profit.
I think thats way too much generalization and simplification of what we are achieving currently here on bitcoin. Yes there are a lot of haters and bashers and a lot of mud sliging has been involved but not all are those some are really just afraid of its is all