Why did Justin Martyr speak so harshly about Christians who ate meat sacrificed to idols?

In his [*Dialogue with Trypho*, Chapter XXXV](http://www.newadvent.org/fathers/01283.htm) , Justin replies to Trypho's charge that Christians eat meat sacrificed to idols by saying that such people serve to show more distinctly who are the true followers of Jesus and exhort them to faithfulness, and that such people are wolves in sheep's clothing, causing schisms and heresies. However, my reading of the New Testament creates the impression that abstinence from food sacrificed the idols was prescribed in the Jerusalem Council (Acts 15) on the basis of the preservation of unity, and Paul in 1 Corinthians 8 clarifies that food does not commend us to God, the idols have no real existence in themselves, but that we should use our freedom to not cause the "weaker brother" to stumble (evidently in this case, the one who through prior associations finds a problem with eating the meat). Paul seems to think that it is more of a question of the company one is keeping that might make the action sinful, as opposed to the action itself. Trypho, as a Jew would have been such a person that the Christians should have at a minimum not publicly ate the meat around, and so they would be guilty of sin. But heresy? Wolves in sheep's clothing? Why does he not argue instead that these Christians are simply guilty of sin?