There was a lengthy ethical discussion about this when GE owned NBC News. Especially when Meet The Press carried GE commercials. Hard to be objective about GE when they sponsor your programming. Yet they were. That's because they're professional.
In this case, there was no proof at all that government funding was being used for news coverage. In fact, it was quite the opposite. The bulk of the federal funding, particularly in the case of WQED, was that it wasn't being applied to news coverage. It was instead being used for children's TV.
I have less of a problem with situations like this. If a program like MTP was not sold out through the normal ad sales channels, the remainder of the funding is (to use an ancient term) sustaining, i.e. paid for by the ownership. "The ownership" in that case is NBC, which was owned by GE (and currently is by Comcast). If the default is for ownership to make up some of the costs of subsidizing the program by running ads for the owner's other businesses, that doesn't seem to me to present an ethical quandary. It's more akin to a
make good situation. If it wasn't that, it would be PSAs or promos, right?
Now if you're being
pressured to use unsold time to run political advocacy ads for the current administration, which is
constitutionally disallowed (see: First Amendment), then we have a problem. The government of the USA and any of its subdivisions
must follow the constitution, and Congress, which holds the sole constitutional responsibility to make the laws, "shall make no law" to interfere with programming decisions or news judgment of any non-governmental entity or person. That is a much more slippery slope.
As for WQED or any other public station/organization,
if they received a specific-purpose grant, and they complied with the terms of that grant and created and/or aired programming consistent with the grant, then they earned the grant and it should not be rescinded after the fact. That's just flat-out thievery. Unfortunately, that is just another tool in the MAGA toolkit.