They aren't unsafe but hybrid airships with the current air passenger transport procedures in place could be even safer. If a HAV goes down with 150 kmh speed and 60% buoyancy there's a better chance the passengers would survive provided there is no pressure loss.
Here's a video of the Airlander 10 prototype crashing:
Here's a video of the Airlander 10 prototype crashing:
https://youtu.be/Mg-RPTiVa_Q