The very basic point that I think everyone is missing on here, is that the knowledge of Quran and hadeeth is a science, and as every science in this word you should have some basic tools to get into this knowledge, not everyone can come and say "Oh I think this hadeeth means such and such "or this verse means such and such until he had acquired some tools.
For example, take mathematics ; you cant put a proposition until you have acquired some mathematic tools, you should have learnt algebra, analysis and studied a lot of other things.
On the same line, to enter or to discuss Islamic knowledge , one must have learned a lot of stuffs before saying his/her own point of view
Thats for a muslim, as for non-muslims then either they should learn or they should start by debating the existence or the non-existence of God IMHO.
And Allah knows best