LOS ANGELES — Arguing that free speech is being stifled at college campuses across the country, a Philadelphia-based advocacy group on Tuesday filed lawsuits against four universities, seeking to force the schools to revise policies that the group says restrict some forms of speech.

The group, the Foundation for Individual Rights in Education, singled out four schools that it says squelched free speech in noteworthy ways — by banning certain T-shirts on campus, for example, or by trying to shut down a faculty blog that criticized the administration — and said it planned to file dozens of similar lawsuits. By the group’s estimate, nearly 60 percent of public universities and colleges have restrictions on rights guaranteed by the First Amendment.

The lawsuits were filed after recent protests at several schools against scheduled commencement speakers, whom some on campus deemed inappropriate. Many of those invited to address graduating students ultimately declined to speak. Also this year, students at several colleges urged their professors to adopt policies warning them about potentially offensive content introduced in class.

“We’re cultivating an intellectually unhealthy attitude that it is not O.K., or even dangerous, to hear opinions that might make you uncomfortable,” said Greg Lukianoff, the president of the group filing the suits. “Universities have been much too shy in saying that there’s a great educational benefit from hearing dissent. You have a whole generation of people who think that they should be protected from anything they see as unwanted or disagreeable.”