With sources Rob, with sources.
If you have a source, your argument will beat the other's who have not.
If someone supposes parents that are unsourced, you can challenge them to produce sources. How I do it here is to post a question, here on G2G about the profile:
Who are the parents of Joe Smith?
Then create the body of your question: Joe Smith [linked to his profile] has parents Johan Smith and Mary Smith but I don't see any sources for these parents. Does anyone have any sources for these parents? If not, I propose that we disconnect them as parents and note them in the research notes.
Then let the Wikitree community do its magic. Someone may even find a source. If not, and no one can show a good reason for the parents, you disconnect them, link them in the bio as disconnected and point to the G2G discussion.
In the future, if someone wants to reconnect them, they need to join the G2G discussion and 'prove' the parents.