The Doubting Thomas

I take a lot of social science classes in school so there are plenty of opportunities for me to get on my soap box and preach about world peace, and I'm constantly amazed at the amount of resistance I'm met with. Recently, one of my teachers accused me of living in a fantasy world, and it hurts. Of course nothing is ever going to change if everyone adopts that sort of attitude! Is it so hard to imagine a world where everyone is able to cooperate with one another? I think not, but many others say differently. I feel like every time I bring it up it gets a little easier for these people to see where I'm coming from, so I encourage you all to spread the message of peace! Has anyone else experienced something similar or am I just crazy?