I think part of the problem is largely calling "right wing", "alt-right", "bigot" any view one disagrees with.

Horseshoe Theory is not true.

Your supporting link says it has no substance - it's a simple meme that is wrong.

This subject annoys me because I am convinced that not only does the Horseshoe Theory have no predictive power - but also that it denies something which really is true - that political violence can come out of the Center aka from Liberalism.

This is a huge blindspot in modern political culture. Conflict coming out of the Center would be a true Black Swan event.