Not a lawyer but I have a good feeling that whoever is doing this has a big stack of cash set aside for settling/paying out libel suits

Some other form of known harm this can bring maybe worth pursuing, but I kind of doubt libel would be a viable option unfortunately. Firstly, I imagine most of these people are in fact making pro Palistine statements, so if that is what the group paying for this truck to drive around is publishing, in that regard, this truck is not really libel. I do notice that the truck specifically references a website called "harvardhatesjews.com", which, if they are stating that these individuals are antisemitic without any other proof than being pro Palestine, then maybe that could be construed as libel. The another major problem is that libel is just plain tricky to get to stick in a lot of instances from my understanding, so even if this was a candidate for a libel case, it may be difficult and expensive to prove. And to that last point, it is difficult for people with little money to sue as going to court in the US (pf which would be the case in this instance) is incredibly expensive. Since most of these kids are college kids, it may be difficult for them to even find the means to pay for a suit. Before anyone says it, yes I know this is Harvard, of which many attendees are from wealthy backgrounds, but by no means is that true for every student. Even for the ones that is true for that also happen to being willing to make a pro Palestine statement, it might not be that their wealthy family is will to back them in a suit such as this.