Critics are spreading alarmist lies about protectionism.

Literal

Critics [topic-は] protectionism [about-について] alarmist lies [object-を] saying [progressive-ています].

人騒がせのうそ — 人騒がせ means 'alarmist, causing a fuss' and modifies うそ ('lies'). 保護貿易主義 is 'protectionism' — a dense Sino-Japanese compound. について marks the topic of the lies.