Thou believest that there is one God; thou doest well: the devils also believe, and tremble.
Misinterpretation: Used to say 1) that Trinitiarian doctrine is wrong, because there is only one God, and 2) that belief is not sufficient for salvation, because if it were then the devils would be saved.
Facts: Trinitarianism (belief in One Being—God–Who exists in three Persons) is not the same as tritheism (belief in three supreme beings or gods). In other words, Trinitarians read James 2:19 and agree with the UPC–there is only one God.
Also, just because the devils believe there is one God does not mean that A) they have placed their faith in that one God for their salvation, or B) that they could be saved even if they did place their faith in Christ. The Bible never suggests that devils can be saved. As a matter of fact, Peter says that at least some of them are in "chains of darkness…reserved for judgment" (2 Pet. 2:4 NKJV). In other words, placing your faith in Christ for your salvation is much different than just believing in one God. Muslims believe in one god, but that does not make them saved. Salvation requires that a person place their faith in Christ (cf. Acts 2:21, Acts 16:30-31, Rom. 10:13).