Yes I agree the ACLU should be (and IMHO is) non-partisan. It's just that if YC appears to fund and partner with the ACLU only when conservatives gain power, that will be negative for YC.
Not if there is some inciting incident that coincided with conservatives gaining power, like, say, a partial Muslim ban. In that case it wouldn't be an attack on conservatism as an "identity" but against certain specific policies that are being carried out by conservatives.
Some good evidence against your interpretation of YC's actions here as simple partisan attack:
* YC did not partner with the ACLU on election day, or on inauguration day, but only after a partial Muslim ban became the law of the land.
* YC quasi-defended Peter Thiel and allowed him to remain as a partner in the face of pretty strong pushback from the left.
