Is there any source that describes the messages in question in more detail?
It isn't enough for me to draw a conclusion, but it's enough for me to question this story which so far has only one side represented. If this comes down to the academic in question making social media posts that tripped FBI/Secret Service's "talking about killing the POTUS" or something similar, then yeah that's going to potentially raise flags at the border.
The rules don't change along with the president after all, just like people doing the same thing with Biden or Obama would have raised flags, this would too.
To be sure we'll have to wait and see the messages that are the focus of concern. What bothers me is that so many here are simply running with the headline and turning off their critical thinking because they (understandably) hate Trump's guts.
Example: Gary Marcus wrote six weeks ago, «single-minded obsession with cutting costs is going to cripple science and American universities, with horrific lasting consequences» - that falls into your «...actions being horrible for research», but how does it fit with your statement of a "good case".
Note, too that last month two researchers (yes, actual researchers) threw bombs at a Russian consulate in France, so the argument that messages are just banter among friends and that academics would never actually do anything 'stupid' has been severely weakened.
I think it would provide better intelligence if the more casual criticisms of policy were ignored and more attention paid to violent/threatening content. This would allow authorities to focus attention on other people involved in the communication which would probably be of more benefit than trying to target all visitors that disagree with policies.
https://www.newsweek.com/french-scientist-banned-us-entry-me...
> The arrest continues a reported trend of temporary visa holders and visitors being detained by U.S. border officials on their way into the country amid heightened immigration enforcement under the Trump administration and concerns that free speech is no longer a defense when it comes to legal immigration status. // [...] U.S. authorities saw these messages as "hate and conspiracy messages," which prompted an FBI investigation that was later dropped. However, the researcher was sent back to France. // CBP's move to deny entry to a foreign national seemingly solely based on their opinion of the president, rather than necessarily expressing ill will or intentions to harm him, comes amid increased scrutiny of those entering the country. // Legal permanent residents, along with those on work-based visas, have been questioned, detained and even removed from the country in recent weeks, including two German tourists and a Canadian woman trying to renew her visa at the southwest border. // Immigration attorneys have begun advising clients to ensure their social media profiles are free of criticism of the administration and images that could be seen as inappropriate or in support of ideas that do not fit with current U.S. foreign policy.
I'm confused: after all, on which bank of the Seine are the snowflakes?