Honestly I think the hate for Vegemite is because people just eat a glob of it and expect it to be good by itself and with a lot of it, imagine if you just ate a glob of ketchup, I bet that wouldn't be much better than vegemite
I've never tried vegemite, but I always think I would like it a lot, I just like bitter salty things that you can use a little bit for a lot of flavour.