It’s quite common for atheists to argue by soundbite. They just assert something in a context where it’s difficult to reply at length. That way, they win, because you (the Christian) can’t adequately defend yourself.
Bible contradictions are usually handled this way. The Skeptics Annotated Bible, for example, just points out so-called contradictions and errors without explaining why those would be errors or contradictions. A more recent example is Twitter user @BibleAlsoSays, who tweeted this:
Let’s play which is correct Judges 1:19 or Joshua 17: 17-18 ? Which is correct Psalm 53:1 or Matthew 5:22 ?
I can’t find the original. I only got it as a retweet from @godispretend. I decided to play.
Judges 1:19: “And the LORD was with Judah, and he took possession of the hill country, but he could not drive out the inhabitants of the plain because they had chariots of iron.”
Joshua 17:17-18: “Then Joshua said to the house of Joseph, to Ephraim and Manasseh, “You are a numerous people and have great power. You shall not have one allotment only, but the hill country shall be yours, for though it is a forest, you shall clear it and possess it to its farthest borders. For you shall drive out the Canaanites, though they have chariots of iron, and though they are strong.”
Joshua was talking to the tribe of Joseph in the verses in Joshua. The events of the battle in Judges described things that the tribe of Judah did. If this was a prophecy (I’m not convinced that’s what was happening here–every general, front line supervisor, head coach, etc., tells his team “You will win! You will prevail!”), it applied to the tribe of Joseph, not to Judah. Joshua was, after all, talking to Joseph and not Judah.
Easy enough. Onward.
Psalm 53:1: “The fool says in his heart, ‘There is no God.’ They are corrupt, doing abominable iniquity; there is none who does good.”
Matthew 5:22: “But I say to you that everyone who is angry with his brother will be liable to judgment; whoever insults his brother will be liable to the council; and whoever says, ‘You fool!’ will be liable to the hell of fire.”
In other words, the Psalmist said that someone was a fool, but Jesus says this is forbidden. The Psalmist sinned! Scandalous. No one in the Old Testament did that, after all! The whole point of Psalm 53:1 is that no one obeys God; i.e. “there is none who does good.” So, if Jesus was giving a blanket prohibition on calling people fools (he wasn’t; keep reading), then the Psalmist sinned in the very song he was composing to say everyone sins, thus proving his own point quite eloquently!
But was Jesus actually giving a blanket prohibition on calling people fools? Look at the context of Jesus’ commands, he specifically says “whoever is angry with his brother,” and repeats “his brother” in the next pronouncement. Jesus is talking about relationships among believers. Many MSS read “whoever is angry with his brother without cause,” which draws some additional lines around the context of this verse. That’s a minority reading, but it appears enough to be worth a mention.
In practice, Jesus himself called many people “fools” and “foolish,” always referring to unbelievers or opponents of his ideology. Brethren, however, in Jesus’ thoughts, deserved more respect than that. Especially in personal, one-on-one exchanges. Public forums are different, which occasionally has to be explained when one Christian calls another out for bad theology (such as the recent James White vs. Ergun Caner situation).
There’s nothing wrong with calling a spade a spade, especially if it grabs the attention of your listener and forces him to see his error. J.P. Holding discusses when parody, sarcasm, or satire is appropriate to use when debating opponents right here. Verses like Matthew 5:22 are not commanding the Christian to become someone’s personal doormat.