If we're talking about the US, that's a straw man. There was a study that made objectively clear that the right is several times more actively violent than the left.
"Both sides" is a euphemistic fig leaf of an argument at best.
If you actually look at the data, that "study" assigned a lot of really unclear or marginal cases to "right wing". They also didn't count a lot of obvious left wing political violence as "left wing".
"Both sides" is a euphemistic fig leaf of an argument at best.