Anduins problem was he needed to realize that there would be no peace with Sylvanas at the head of the Horde sooner.
Alright, then try this one on for size: If you see a race that you have fought against or has given you issues in the past come onto YOUR land, do you let them set up shop or do you try and get them off your land.
The frostwolves might not have fought against the Dwarves in a full fledged war, but they might have seen them before and alongside humans. For all they knew the dwarves could have been an allaince scouting party or forward advance.
What you are saying is the frostwolves should have let a potential enemy force come into their vally and do nothing. Hell, for all we know, the Dwarves might not have been noticed unless they were in areas the Frostwolves were using to hunt or, since Drek’thar is a shaman, he felt/heard the land cry out in pain from the Dwarves digging.
It is not clear who threw the first punch in Alterac, but the fact that both were there was enough to set up conflict between the 2.