how can knowledge misguide someone?

It is a common fallacy that the more knowledge you have, the more guided you are.
This is not always the case - there are many examples of knowledgeable people throughout history - scholars, rabbis, scientists, IBLIS, etc - that erred and were misguided - even though they possessed more knowledge than most

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The misconception comes about because, the more someone is guided, the more knowledge they will acquire - and hence a guided person will become more knowledgeable.
Every guided person will have knowledge (not be ignorant about whats important)
BUT not every person with knowledge is guided!

All doves have wings,
but not everything with wings are doves (some are bats!).

The doves are those guided by their Lord
the bats are those in darkness and error
the wings are knowledge that allow both to fly
but only the doves will fly straight
the bats will fly in circles

Why is that you ask?
the bats are seeking the knowledge for the sake of knowledge -
knowledge is their goal!
but to the doves the knowledge is merely a tool - not the goal
the goal is Allah swt - to love Him swt  - to serve Him swt - to mention and remember Him swt
and their wings of knowledge simply help them to fly to their goal

The wings (knowledge) will allow you to fly
but it will not give you DIRECTION

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In fact, sometimes knowledge can contribute to the misguidance.
Sometimes, when a dove gets its wings,
it becomes distracted by his ability to fly
and stops heading toward the place he was intending to fly
then night comes
and he flies in circles
becoming a bird of the night
and thus becoming blind as a bat

To illustrate this in another way
A blind man can find his way to his beloved wife
but when he regains his eyesight
he starts getting distracted by all the other beautiful women
and forgets about travelling to his wife
and strays
by having more knowledge (from sight)
he was more misguided
than when he knew less of the world (blind)

This doesn't happen to everyone
but it simply shows you that KNOWLEDGE is not the answer to AIM for
it is a tool
and like all tools
it can Benefit you if allah swt allows it to
or it can distract you if allah swt allows it to

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Is a bat that can fly
any better than
a rat that cant fly?

Is a misguided person with knowledge
any better than
a misguided person without knowledge?

many waste their time seeking nothing but knowledge
but without seeking Allah swt and His swt guidance
Why?
is there any important difference between a rat and a bat?
is there any important difference between a misguided scholar and a misguided layman?

If anything

Isnt the misguided scholar worse than the misguided layman? Because many will look up to the flying bat (misguided scholar) and become misguided by following them. 
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Conclusion:
- if you seek knowledge first and foremost
- yet lack an intimate communication with your Lord swt - then question your motives - question your aims!  are you seeking Him swt?  or do you just want to be with those that fly? (i.e. the scholars).  if so - then Not all those who fly are doves!! so beware.

Instead
- seek Allah swt and ask Him swt to guide you
- then the knowledge that you need - that will benefit YOU - will come by His swt permission