(a)Offense.—Except as provided in subsection (c) of this section whoever—
and thereby obtains, alters, or prevents authorized access to a wire or electronic communication while it is in electronic storage in such system shall be punished as provided in subsection (b) of this section.
In other words, if something is preventing you from accessing content, bypassing it is a violation. Blocking ads itself isn't a violation, but blocking something that hides content unless you turn off ad blocking is.
UNIX was not designed to stop you from doing stupid things, because that would also stop you from doing clever things. -- Doug Gwyn