Interesting question. A question that has been repectedly asked
for decades, almost since the birth of tanks.
I advice reading "Panzer Leader", a copy I saw recently at
Border's.
It is by none other than the grandfather of German lightning
warfare Blitzkrieg, Guridian. He had an arguement of why you still
need tanks even when they are not totally invulnerable.
The answer is in tactics. Namely, massing of armour, surprise, use
of terrain, attacking the weak points of defense, movement shifter
than the enemy can recover.
Tanks are just tools. Anyhow use a tool wrongly, you wouldn't get
the desired results. Use a tool correctly, you would get the result
the tool is designed to perform.
If you don't fear tanks, then you have never been an infantry
trooper seeing tanks in action 
