It just strikes me that if a large company like hikvision was selling compromised devices, it would only be a matter of time before it was discovered and their market share would drastically plummet. No one would ever trust them again. Can't see them risking it.
Being smart about security is as much about responding to threats as it is reducing the possibility of a threat. We don't know what we don't know. Also remember that this is China we are talking about. The government controls everything to some extent or another. Companies don't have the protections we do here. Not that we are perfect
If the Chinese government wanted Hikvision, or Dahua, to implement back doors they would probably have no choice. I imagine the same might apply in the US as well however I would hope it's less an issue of coercion and threat than agreement and cooperation.
In any case the best prevention is to assure you have no risk in the first place. I've watched the transformation of the military from proprietary systems to COTS over the years and my biggest concern is the risk this introduces as in a COTS system it's impossible for the government to control the design and manufacturing process completely enough to have a high level of assurance that there are no backdoors.