Rhetorical evasion

It is a red herring.

A Red Herring is a fallacy in which an irrelevant topic is presented in order to divert attention from the original issue. The basic idea is to "win" an argument by leading attention away from the argument and to another topic.

nizkor.org

...something correct, agreeable, or even tautological

A thought-terminating cliché, you mean?

When a commonly heard and accepted phrase is rhetorically introduced as a substitute for an actual argument. _{(logfall.wordpress.com)}

From Wikipedia's List of Fallacies:

Thought-terminating cliché – a commonly used phrase, sometimes passing as folk wisdom, used to quell cognitive dissonance, conceal lack of thought-entertainment, move on to other topics etc. but in any case, end the debate with a cliche—not a point.

Examples from Logfall:

• The phrase “Only God knows” is often interjected at the end of a discussion to imply that no one is justified in taking a position on the issue, or to assume the evidence is balanced on both sides.

• Sometime the phrase “Freedom is not free” is used to justify initiating or entering a war.

• Christians often quote the verse “The fool has said in his heart, ‘there is no God’” sometimes as if this is a justification for belief in God, and sometimes simply as a thought-terminator.

• When having their expectations questioned, older people often, due to either having no real answer or having no interest in giving an answer, say “When you’re my age, you’ll understand.”