muddy the waters
Confuse the issue, as in Bringing up one irrelevant fact after another, he succeeded in muddying the waters. This metaphoric expression, alluding to making a pond or stream turbid by stirring up mud from the bottom, was first recorded in 1837.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.