Music question: Who do conductors think they are?

I sometimes watch culture talk shows on television where there is talk about the way a certain conductor conducts his orchestra to perform a certain symphony.
The one conductor wants a certain passage to sound loud(er) where an other wants it to sound soft(er), or where one plays a part fast(er), the other plays it slow(er).
Assuming that the composer meant his piece to be played in a (his/her) specific way, who do conductors think they are to violate the meaning of that composer?
Are they artists too?
Do they want to measure themselves with the great minds that composers are/were?
Or am I simply missing something important?