A doctor in CA explained to me that they have fewer hospitals per capita than most states, because years ago they were required to conform to more strict earthquake codes, and many hospitals closed rather than adapt or rebuild. They thus had the minimum hospitals for normal times, and obviously far too few for a pandemic. That's why the transmission rate in CA is similar to other states, but the hospital situation is more dire, and so they are more worried than other states about having more cases. They really did need to flatten the curve.
I agree that there is very little risk from playing baseball. College students don't have much risk, either, especially if they are being tested often. But, I guess every infected person can lead to a hospitalization somewhere down the line.
The point of the petition is that the majority of other states, nearly all of which have far less resources than California, have figured out how to resume high school athletics. Our elected and appointed officials should be acting with urgency to return athletics to our high school age population to improve their physical and emotional well-being.