Is there any word for a person who always blames others even if others are not wrong.

Several dictionaries give the word 'blamer', seems to cover what you asked for.

Particularly if the person knows the accusation is false, he is a
Slanderer / Libeler / Defamer
Calumniator

If the accuser is himself guilty of the accusation, then he may also be a hypocrite.

I would reject all these since blaming others is not a necessary part of any of these. They may be true about the person in question but they do not define them.

To blame is not a very active verb, to accuse ìs. Maybe not well defined, but I mean to say I agree. (smilo)

Huh. I was looking for an antonym for scapegoat, and there doesn't seem to be one. Good question!

Scapegoat

The scapegoat's is a complicated story. A bit hard to want an antonym for a goat that's chased off to the desert, poor thing.
It's biblical, we call it sinbuck. (ant. gracegoat? )

Even in its metaphorical sense it can be kind of tricky finding its antonym. Would it be someone who takes the blame deservedly? Someone who doesn't take the blame when it is deserved?

Put the Blame on Mame, boys. Put the blame on mame.

The Lady known as Lu

always pointing the finger
constantly passing the buck

It is not always the boys who put the blame somewhere.

As already admitted in that pretty song one page back.