Does every act of self defense automatically classify someone as a murderer?

No. Acts of self defense happen every day, and the vast majority do not have people calling them a murder.
This is an incredibly disingenuous statement that is ignoring the facts around this specific case of self defense.

BTW, for the record I’m a leftie progressive.

Irrelevant. Ad hominem. Whether or not you’re a leftie has no effect on the strength of the argument you are presenting.

the events that led to the death of those people that day was due to self defense.

Rittenhouse did manage to engineer a situation in which everyone involved had a credible claim of self defense. I will point out however that one of “the events that led to the death of those people that day” was Rittenhouse deciding to go to a town he had no good reason to be with the stated goal of “protecting property”.

If a criminal breaks into someone’s house and the owner charges at them with a baseball bat the criminal is “acting on self defense” if they shoot the owner. The criminal still shouldn’t have been there in the first place and the entire situation is the criminal’s fault.
Now replace the criminal with someone who had a grudge against the owner, and broke in hoping this would be the outcome. The legal system would only find them guilty of breaking and entering, but that person is a murderer.

Anyone who disagrees needs to establish they know the facts

The fact of the matter is Rittenhouse’s stated reason for being there with a gun in the first place was to “protect property” from people who were protesting the murder of George Floyd. Because in his mind it is acceptable to shoot people to protect property, it is not acceptable to damage property to protect lives.

Can you demonstrate why it wasn’t self defense?

It’s both.
Yes, legally Rittenhouse was acting in self defense. He is also a murder who went there with the hope of being able to insert himself into a situation where he could kill someone.