I think this knife thing has been asked before.
There are guys here walking around with 3 foot machetes. Most of them use them for work, others use them for killing their brother in law, cousin, drinking buddy, or who knows who or what. It is a tool and a weapon and I have never seen a cop stop anyone from carrying a machete. Never.
A gringo walking around with a hunting knife is another story.
First, you are a gringo and you stick out like a sore thumb no matter how hard you try.
Second, a cop is going to look at you like an easy mark and he knows he can lean on you and leave you worried.
You are in his town and he can do what he wants with you. He knows you don't need that knife, but he also knows that you feel you need to have that knife. See where this is going? This is what Pirate was getting at with the taxi comment.
So, if you have a knife in a tankbag, and you are searched, nobody is going to give a damn, they might comment on how much it costs, the workmanship, where you got it, but they are highly unlikely to take it from you or hassle you unless you are coming off as some kind of macho blowhard. They can spot bullshit a mile away, just like anyone here can spot a gringo a mile away.
Carry tools you need. If you feel you need a tomahawk axe for camping, then carry it in your panniers. If you need a knife for camping, ditto.
The chances of you surviving an encounter where you have found yourself having to actually use it as a weapon are slim to none, it doesn't matter if you are Bruce Lee reincarnated or how well you have been "trained".
People who will hurt you here do it for a living.
Day in and day out, and you are their meal ticket.
They have survived in a rough game and are better than you. It's like anywhere else in the world.
So you avoid those people. Very simple to do. If you can do it Friday at midnight in Compton or downtown Detroit, you can do it here. It is called common sense. Not to mention that you will likely be outnumbered.
Take a look at the case of the late Peter Zarate. Google him and read the story from the New York Times. He was an ex-Seal. Are you an ex-Seal?
One thing I have learned about Mexico, is that it is really not that complicated, but we, as gringos, tend to make it way more complicated than it really is. There is a fluidity to life here that you have to tap into and let yourself go with it, surrender yourself to it when you find it. Resistance is futile. That will let you find the good here and more importantly, it will help you spot the bad.
If you find yourself on the wrong end of things, your instincts will kick in and you will do what you can and the outcome will be what it will be. Learning to avoid the wrong end of things is the trick, and you'll do that better from within the flow than from outside the flow. I think anyone who lives here will understand how difficult it is to describe this, it is a feeling not a procedure per se.