Can you contradict someone else?

Yes

I contradict what others say, all the time. they are wrong, and I tell them.

Yes. You can contradict someone else besides yourself.

Contradict just means 'deny, rebut, or dispute'.

It's just more ironic when you contradict yourself.

My chief perception of "contradicting" is when somebody contradicts somebody else; the use of "contradicting oneself" is minor. Thus your question rather surprised me. Note that I am an oldish Briton.

no you can contradict anyone

Yes.

I do not want to contradict anyone, but I know what I am talking about.

In the field of psychology, cognitive dissonance is the mental discomfort (psychological stress) experienced by a person who simultaneously holds two or more contradictory beliefs, ideas, or values. The occurrence of cognitive dissonance is a consequence of a person performing an action that contradicts personal beliefs, ideals, and values; and also occurs when confronted with new information that contradicts said beliefs, ideals, and values.

https://en.wikipedia.org/wiki/Cognitive_dissonance

self-contradiction - contradiction of oneself

https://www.collinsdictionary.com/dictionary/engli...

Contradict yourself!

Why it is good to say the opposite of what you just said

https://www.fastcompany.com/3067169/how-your-brain...

"contradicting yourself" is the joke version of this idea.

Sure you can.

https://www.google.com/search?q=contradict+definit...