Can you expand on this? Trusting a VPN is equivalent to trusting the VPN provider. As long as you believe the VPN provider is more trustworthy than the network you're tunneling through, I don't see why trusting VPN is bad practice.
The Military might not care about people knowing they are talking, just what they are talking about. In that case, using a VPN makes sense because they can tunnel traffic to a server that is exposed to a private network and use a central chat server there or something. All traffic to that central server would be encrypted.
You'd have to use a technology like TOR to get closer to real anonymous communications on the internet (although even that isn't perfect).