Presidental decrees not so easy
It seems that some, particularly the University of Texas at Austin president Larry Faulkner, a chemist, did indeed stand up and be counted. But the political issue is somewhat more complex.
American universities rely for their funding from political sources, such as states. This is something that we in Australia also deal with. But unlike Australia, and I am guessing universities in the UK and elsewhere, American universities can be subjected to political pressure to revise or restrict what is taught. There is, for example, that really stupid piece of legislation in Florida designed to "stamp out leftism" and force teachers to include any theory a student might like to see taught, in particular Intelligent Design. [If it gets up, I really hope a Holocaust denier uses it to sue for a change in curriculum.]
A university president is first and foremost a political beast under such constraints. They are there to see education given at the best level they can, and to see academic work done the best it can be, and this involves a fight for resources. While I am sure some presidents behave in a less than idealistic manner, to assert that it is policy that a university "believes" in evolution is to take at best a self-defeating stance in areas where the presumption is that education is something that can be squeezed for political purposes.
And on reflection, I am not sure that Rennie is right anyway. Suppose that a university did declare that it supports "evolutionary theory". Which kind? Does it support neo-Darwinian theory as revised by Richard Lewontin? John Maynard Smith? Ernst Mayr? Does that mean evo-devo is not to be taught? Shall we condemn ideal morphologists as schismatics and heretical? Science is all about changing ideas to suit evidence and experience, not asserting doctrinaire assent.
Universities ought to acclaim the right to teach the best ideas in a field, and that is all. If an idea is popular outside a university, but it has been closed off by scientific and scholarly research as a viable option, like phrenology, platygaeanism, or phlogiston, then it ought not to be taught. If that offends the agendas of religious or political figures, then they have the same rights to argue their case as anyone else. Who knows? Perhaps some of them will actually change the scholarly debates for the better. But they have no right to impose doctrine on scholarship, and neither do university presidents.
I'm going to come down all Millian liberal on this one.