Twisted Treeline: What am I missing here?

So I decided to go into a Twisted Treeline 3 vs Bots game tonight to do something new and different. Everything I've seen about this is "Fast Paced, not a lot of strategy, get ready to gank and be ganked at a moment's notice so don't be Squishy." So that's what I do. It's the Beginner Bots, so not particularly difficult, and about 7 min in we've essentially destroyed everything but the Nexus. But then my teammates tell me to pull back from the Nexus just as I start to attack it... so I back off, killing Minions as I leave 'cuz why not? The minions that were with us finish off the Nexus, we win - and suddenly I'm being called an Idiot and told that one of them wishes my mother would die of something censored.

Being a newb to LoL, I'm quite used to being abused by other players - but that's almost entirely in situations where the team is losing or I'm unintentionally feeding. (or where I called Bot, someone immediately after me called ADC, and they decided that they called it first and when I wouldn't yield Bot to him, he was an arsehole the entire game) So getting this kind of shit for winning a game too quickly - what am I missing here?