I wish it were a fix-it, and that's what shocked me the most. It's a full fledged moving violation, citing 625 ILCS 5/12-610.5:
The guy must have been having a bad day and/or was pissed about traffic. He was pretty much a jerk throughout the whole encounter.
Sec. 12‑610.5. Registration plate covers.
(a) In this Section, "registration plate cover" means any tinted,
colored, painted, marked, clear, or illuminated object that is
(1) cover any of the characters of a motor vehicle's
registration plate; or
(2) distort a recorded image of any of the characters of a
motor vehicle's registration plate recorded by an automated
red light enforcement system as defined in Section 1‑105.5
of this Code or recorded by an automated traffic control system
as defined in Section 15 of the Automated Traffic Control
Systems in Highway Construction or Maintenance Zones Act.
(b) It shall be unlawful to operate any motor vehicle that is
equipped with registration plate covers.
(c) A person may not sell or offer for sale a registration plate cover.
(d) A person may not advertise for the purpose of promoting the sale
of registration plate covers.
(e) A violation of this Section or a similar provision of a local
ordinance shall be an offense against laws and ordinances
regulating the movement of traffic.
(Source: P.A. 94‑304, eff. 1‑1‑06.)