"Specious" means superficially plausible, but actually wrong or false. It describes something that appears to be true or good on the surface but is not so in reality. Therefore, "False but seemingly plausible" is the closest meaning.
Believable and compelling: This is the opposite of specious.
Too technical to understand: This relates to complexity, not deceptive plausibility.
Harsh and accusatory: This describes tone or intent, not the truthfulness masked by appearance.