It is a personal vendetta because this dude is a reject. Thats politics, any politician will work towards his interrests.

Politicians could try to settle personal scores with individuals or institutions when they have the oppurtunty. But there is no evidence or evidence that Baron Trump was rejected by Harvard, Stanford, or Columbia. This rumour emanated from the social media.
However, Trump should consider the effect of these freezing of funds on research and development that will benefit the US society. Many industries depend on the discoveries of these universities. These institutions should also seek for alternative funding to finance their projects. In less than four years, a more friendly government might emerge.