SS. you will find it very difficult to prove all those great names you've mentioned are better than murali. may be some of them but not all.
Aside from Bradman, no one can 'prove' anything. You give your evidence, and other people can accept or reject whether its good enough. I hope that some people would come over to my way of thinking if they keep an open mind about it, but they may not, and that's fine too. And they may be right - I don't think so - but you can hardly do a controlled experiment in sports.
I can give evidence why they are better, but whether that is good enough to counter what people think or the evidence that people can generate to support their own position is up to them.
There are several batsmen who are crap against spin, then there's the matter of averages, .
Let's say you have an all time middle order of Tendulkar, Lara and Richards. Two of them have generally belted the two spinners in the side. Neither of them have really belted McGrath, for example. They may have won some battles or lost some, but at worst the all time great pace bowlers are even.
So called "all time great spinners", on the other hand, lose out vs. both. So you tell me who you'd rather have bowling against Tendulkar and Lara: McGrath/Marshall or Warne/Mutalitharan. If you decide the latter, that's fine and that's up to you.
I'd take the former every time. If you're talking about crappy players of spin, its one thing, but they're rare in an all time side. All the players are great players of pace as well, but its very instructive how the best fast bowlers still manage to get the best batsmen, while the best spin bowlers have a tougher time.