Well I am a dedicated cyclist, but I also have a motorbike licence and in the past was a dedicated biker. Where I used to find myself at the head of a queue of cars during the London morning commute, I now find myself in the same place with a bunch of other cyclists. My cycling confidence is undoubtedly down to my motorbike training (which was much more rigorous than my training when I took my car licence btw).
I don't actually feel that differently about either - both groups are more vulnerable (as opposed to dangerous) and I don't have a problem with bikers in the bus lanes myself.
It's definitely not helpful if two-wheelers start fighting amongst ourselves though. Sweeping statements such as some of those Corkie has made is completely pointless tbh.... not to mention inaccurate - For example, personally, I have been unable to filter through due to motorbikes on a number of occasions - this is entirely logical as motorbikes are bigger and unable to get through the same gaps as their smaller engine-free cousins. To be honest though, I'm not going to get that wound up about it or translate that into some kind of "rarely, if ever..." style sweeping statement - we're on busy roads and we can't all have it our own way the whole time.
So in essence - we need to learn to share a bit better and stop being quite so territorial and ready to point the finger!!