In lieu of having anything useful to add, when someone expresses an opinion or tells you something, it is perfectly acceptable to reply with a stock meaningless phrase:
Example 1:
John: I think Ralph Nader should be killed and made a saint.
Bubba: Y’know? — I have nothing to contribute
Example 2:
George: Def Con 1! Open the soap duckets, take to the sword!
Colon: There you go. — I wonder what my voice sounds like now, I haven’t said anything in the last 20 seconds