Private property implies ownership. The moment you assume ownership, you have to be ready to defend your claim against a counter claimant. How you defend this claim depends on where (and when) you live, but almost uniformly requires force - either directly (violence) or indirectly (court systems and police, aka violence by proxy).

If there is no concept of private property, the need to defend ownership ceases. If no one owns anything, there can be no claims - and counter claims. Like a happy family where your brother's meal is also yours, and vice versa - depending on how hungry you are.

For the record, I don't support the latter stance and believe Marxism is catastrophically ignorant of innate human tendencies. But as an ideology, it is worth exploring to reexamine our own relationship with and understanding of private property.