I use 3L plastic apple juice jugs for starters. If I couldn't properly sanitize the starter vessel, there's no way I could sanitize my better bottles or pales either. Knock-on-wood, I've never had an issue with infection I could trace back to the starter.
I alternate between starsan and an acidified bleach solution. I did run into an issue a few years ago where I was only using starsan and developed a house bug, so mix up your sanitizing media if you're relying on sanitizing, not sterilizing.
I've always heard that, to avoid infection, when you pitch into wort, the idea is to have the yeast outnumber any bugs. If you're pitching, say, a smack-pack into 2L or 4L, that's a much higher pitching rate than a 2L starter into a 20L batch. So by that logic, a starter should be more safe from infection than a whole batch. Am I missing something here? I know hops are slightly antibacterial, but besides that, what else is going on?