"Relativists employ the law of non-contradiction and the law of cause and effect whenever they talk about their belief in relativism and its relation to the world... People keep saying all is relative, when they know their very thinking and talking involves principles that are not relative."
In other words, as soon as someone attempts to communicate they assume enormous and far reaching absolutes. The first assumption (law of non-contradiction) is when they say they have A in their pocket that it does not mean they have non-A. The second assumption (law of cause and effect) is when they speak (cause) it will have an effect (communication). Now, these assumptions really start to matter when someone attempts to communicate their beliefs because they make more assumptions on top of the first two. They may assume that right and wrong exist, or that altruism is good and exploitation is bad. So when you communicate your worldview or defend your beliefs, you are admitting absolutes and meta-standards exist, even if you think they don't. Piper puts his finger on the motivation behind embracing a self-contradicting non-standard standard like relativism.
"People don't embrace relativism because it is philosophically satisfying. They embrace it because it is physically and emotionally gratifying."