The Free Public Transit advocates make some very good points. I've disagreed with them before. But I think even they would agree that there are limits to how much transit should be subsidized, and to what should be free. There are also limits to what level of service should be subsidized.
There seems to be a fairly strong consensus for a minimal level of transportation subsidy. If a road or sidewalk is available, it's usually free to use - assuming you supply your own power. In the past, residents have sometimes been expected to maintain their own roads, especially in remote areas, and it gets more problematic when water is involved. But at the very least, people seem to agree that the government has the responsibility to maintain clear public rights-of-way on land, and to keep them relatively crime-free. Only the most extreme libertarians would argue that every individual should pay for the full cost of maintaining and policing all the streets they use, without any governmental tax or fare collection.
On the other hand, if I wanted to spend the rest of my life shuttling back and forth between Irkutsk and Tristan da Cunha, in the greatest speed and comfort attainable with our current technology, should I be able to do that for free, at government expense? My guess is that even the most die-hard free-transit activists would say no.
So I think the vast majority of people reading this can agree that the sidewalk in front of your house should be free (whether subsidized directly by the government, or indirectly by unfunded mandate) and that high-speed, multiple frequent luxury trips to the South Atlantic should not be free. There's a lot of gray area in between.
In fact, "transit" usually refers to short-distance public transportation, and our respected colleagues at freepublictransit.org specifically say that they want to "Remove the user fee [fare] from urban buses, trains, trolleys, street cars, and light rail." (My emphasis.)
Where do you draw the line? (I'm not telling you, I'm asking you.)