Yes, it is perfectly legal for you to publish screenshots in an article/blog post that is discussing the content of those images. This is considered to be within fair use doctrine under section 107 of US copyright law, "Limitations on exclusive rights: Fair use." Here are the four conditions given that determine fair use:
(1) the purpose and character of the use, including whether such use
is of a commercial nature or is for nonprofit educational purposes;
(2) the nature of the copyrighted work;
(3) the amount and substantiality of the portion used in relation to
the copyrighted work as a whole; and
(4) the effect of the use upon the potential market for or value of
the copyrighted work
So long as you're not trying to make money off of someone else's work, publishing screenshots for discussion is legally protected free speech (national security issues aside, of course).
Disclaimer: I am not an attorney.