The last time I gave a 20 minute presentation, it had to be cut off two thirds of the way through after we reached the 45 minute mark. And that was after I cut out a lot of the additional explanation around slides, and basically just started reading them off. I'm not really afraid of giving presentations. But it's utterly pointless for me to do so - people can get literally 4x the information in the time from just reading. But don't let it bother you. You're classmates are arseholes and don't understand what it's like.