If it comes to it,
Lemmings 2: The Tribes → Lemmings (video game) → Richard Wagner → Adolf Hitler
is shorter. 
What you need to do is find a two-step link.
(Incidentally, even if you take out the trivial solution of going via Lemmings, I can find the three-step link
Lemmings 2: The Tribes → Cannon → World War II → Adolf Hitler
so yours still isn't the shortest 
)
It's been a while, but I thought I'd update with a couple of other ones:
Lemmings Paintball → Catapult → World War I → Adolf Hitler (3)
Lemmings Paintball → 1996 → Hitler Youth → Adolf Hitler (3)
Lemmings Paintball → 1996 → Artur Axmann → Adolf Hitler (the guy was the leader of the Hitler Youth and died in 1996) (3)
Christmas Lemmings → Christmas → South Tyrol → Adolf Hitler (3)
Oh No! More Lemmings → Sic → Appeal to ridicule → Reductio ad Hitlerum → Adolf Hitler (4)
Oh No! More Lemmings → Tutorial → Woodrow Wilson → World War I → Adolf Hitler (4)
Oh No! More Lemmings → Amiga → Japan → World War II → Adolf Hitler (4)
Oh No! More Lemmings → Amiga → Marilyn Monroe → (has the word "Hitler" in the text but not link
" title="Angry" class="smiley" /> )
Oh No! More Lemmings → Amiga → Czech Republic → Adolf Hitler (3)
All New World of Lemmings → Buzzard → Common Buzzard → Japan → World War II → Adolf Hitler (5) (or via Amiga, same as ONML)
Had enough now. I just used a tool to find the opposite way:
Adolf Hitler → Russia → The Nutcracker → Lemmings (video game) (3)
One other interesting one I found:
Lemmings → Rockstar North → Daily Mail → Adolf Hitler
