Hey OP, if you don't want to buy Bitcoin any longer then it's your choice ,that won't make others to stop buying it, there are lots of people who will continue buying it and everyday lots of people keeps getting in.
Moreover FYI, what you have said here is wrong, of course I have heard about the 51% attack or whatever they call it, but that's not enough reason for me to quit. People keep on imagining things that are never even going to happen. A lot of people come up with these as a way to discourage others from taking part in buying Bitcoin.
I agree, your reason is useless and cant stop people from buying bitcoin. What you have said is somehow opposite to the reality. In fact many people get profit on it. If bitcoin was a crap then it wont have a value now. But since its not, it is still valuable and helpful to anyone who have it.