What Anti-Trinitarians quote:

A variety of possible things, however this quote is included because Enslin makes a comment on Justin Martyrs view that the similarities between pagan and Christian practices were the result of demon activity.

What they fail to tell the same article also says:

Morton Scott Enslin commented about Justin's view: "That Christianity was so regarded [as just another mystery cult] is perfectly clear from the pains Justin Martyr takes to prove that these resemblances between Christianity and the other religions were all due to the malignity of the demons. These wretched demons had read the Scriptures and had realized, although imperfectly, what was destined to be. They trembled as they saw their coming overthrow and realized their helplessness to prevent it. To salvage as much as possible and to delude men they hastily concocted rites and ceremonies as near as possible to those they foresaw were to be instituted. Thus they hoped that when Christ appeared and instituted his worship men might be deluded into believing that the Christians were borrowing from older pagan ceremonies and beliefs. To the modern student this explanation of Justin may seem most naive; none the less, it is highly important as incontrovertible evidence of the growing likeness of Christianity to the other cults which made such an explanation essential." (Morton Scott Enslin, Christian Beginnings, Part 12, p 191)