Eveybody wants warfare to be asymmetric and biased towards them- why would we want to give a potential adversary perfect information about what weaponry we have as well as its exact capabilities? Unfortunately, when you want to keep a secret, you can't tell all of your citizens and trust that they won't tell anybody...
There can be. But secrets can also be unimportant, or easily learnable through other public means. We need to analyze what we're keeping secret and optimize.
The democracy answer is omni-present. People can't really be said to support something they don't know about and if secrets encompass too much of their government it becomes, for practical purposes, illegitimate.
The cost of keeping the secret has to be weighed along with the cost of it leaking and the chance of that happening. It's not practical to keep everything a secret for reasons of censorship limiting other valid activity or just the increased bookkeeping in tracking secrets without revealing them.
And ultimately, not everything is all or nothing. You can have an undisclosed number of weapons for instance, but have a process where civilians can band together and form a special body, get some people vetted, and be granted access to otherwise secret information that they, because of their unique skills or interests, may have input on. This exists today in the form of aerospace companies, etc, who have access to many secrets to aid in the planning and construction of further tools.
To be fair and let the best win? There is just no honor anymore.