While previous M's (maybe up to the M6 but, I think, more likely, the M4) were definitely (or could definitely) be seen as being used by Photojournalists; the advent of auto focus and auto exposure basically killed the M as the photojournalist's tool.
That said, I don't recall Leica marketing the M8 as a photojournalist's camera.
All I know is, I bought an M8 earlier this year and I knew that I was getting an M but that doesn't mean I'm going to swing it around in my arms in the rain or snow or desert heat - it's not an M3 - it's got much more electronics in it and such.
WRT a $5000 camera not having weather sealing on it - That depends on what it's designed to do. Clearly the Canon 1D series cameras are meant to be rugged tools (and photojournalists do use/abuse them that way) - as such, they have the weather sealing built in. The M8, as I stated, was never marketed as a photojournalist tool and therefore does not have any weather sealing.
Dave