The burden of proof is on those claiming the bus option is safer, since they're the ones proposing a change in the name of safety. It's very hard to disprove since the necessary statistics aren't available, but that's immaterial since Anderson never proved it in the first place.
Here's what I found. Based on what I could find on the National Transportation Database, buses appear to have less fatalities per passenger mile than intercity trains do. It's plausible that Anderson sees something similar, and truly believes without PTC that trains will be more dangerous than they could be, and doesn't want to carry that liability/risk.
There's also plenty of people that are claiming that buses are more dangerous than trains. That also requires the burden of proof to be on the person making the "more dangerous" accusation, and so far I haven't seen any hard data, at least on the US side, to definitively prove that trains are significantly safer than buses. (Which, by the way, if we're going to take safety as the primary goal, then let's force everyone to fly. That's safer than both, based on what data seems to be available.)
For me, I'd rather focus on getting people out of their own vehicles and onto safer, more sustainable forms of transport. Buses serve as a vital link in many of those areas, and I fear the rhetoric around buses being more dangerous than trains will lead people to a (very false) conclusion that since there's no train on a particular route, they might as well just drive themselves since buses are (in their mind, fed by rhetoric that buses are more dangerous than trains) just as dangerous as driving. It may also lead to legislators not willing to fund those bus links in areas where we do need them, and where we can use them to either serve local needs that a train can't easily serve, or work as a feeder system into train routes.