Palliate, extenuate, gloze, gloss, whitewash, whiten are comparable when they mean to give a speciously fine appearance to what is base, evil, or erroneous.
Palliate may stress the concealing or cloaking or the condoning of the enormity of a crime or offense. The word also is used especially in reference to other than moral evils in the sense of to disguise the true nature or extent of so as to soften the bad effects.
Extenuate (see also THIN ) implies the aim to lessen (as by excuses or explanations) the seriousness or magnitude of some crime, offense, or guilt. But the term is often used in the sense of to make excuses for.
Gloze and gloss often followed by over, imply an aim to veil by more or less light dissembling (as by specious comments or by flattering talk) the true harshness, unpleasantness, or disagreeableness of something; often, the words suggest a representation of what is actually disagreeable as more or less agreeable or as not distinctly unpleasant; gloze, however, is usually more derogatory than gloss which is a relatively neutral word.
Whitewash, and less often whiten, imply an attempt to cover up (as a crime, a defect or fault, or a person's guilt) by some such means as a superficial investigation, or a perfunctory trial, or a special report that leads to a seeming acquittal or exoneration or that gives the person or persons accused an appearance of innocence or blamelessness.