I think the best defence for universalism, against the tradditionist is the fate of the old testament prophets
For according to the traddionist theology people like David, Solomon, Daniel will have to burn in eternal hell.
For these men die without knowing the salvation of the cross.
Even though these men knew God, the sacrifices of animals did not take away the sins according to Paul.
They probably come up with things such as, it did not apply to them for Israel were Gods chosen people, but then wouldn't God be breaking his idea of being no respector of persons.
Jesus said that there were no greater, than John the baptist born of women, but yet he that is least in the kingdom of heaven is greater than he.
Also I remember Paul saying that how we are given a better promise than the old saints, who had to endure the persuctions, yet did not receive the promise.