How should a person assertively open his or her mail? Is it enough to just rip it open? No. A lot of times, stopping right here, at the point of being about to open the mailpiece, is the most assertive thing that a person can do.
There are two reasons for this: support and protection.
Support. Some mail is tougher to open than other mail. Major tax bills, envelopes that say "disconnection notice" or, worse, "eviction notice", or letters from long-estranged family members fall into this category. Sometimes a company or a person will send a letter rather than just calling the person - it is easier to write a letter than to actually face the person over the phone. That leaves the recipient (who may be living alone) to just open the envelope themself, read the contents, and then agonize alone over how to handle whatever the problem is. No! There is a better way! Ideally, the sender would have at least called to give the recipient a head's up about what's heading their way, but if that hasn't happened, just call them. First, before opening the envelope. That way, you have the sender's support, on the phone, while you are opening the envelope, and you can talk to them about it right then. It's amazing how much easier this makes almost any problem.
Protection. If you have this mail policy in place, then if you ever receive an unexpected piece of mail, with no return address, you will not be pressured by curiosity or for any other reason into actually opening such a mailpiece. You might want to save it, but you won't open it. Why not? Just like spam in e-mail, it's an unexpected piece of mail that could be negative, but even more, I know it seems unlikely, but you might have received an actual piece of blackmail. It is very rare, but the threat of it may not be as rare as we think, that a blackmailer releases an envelope with disparaging pictures (whether real or faked) to "punish" a person who has chosen not to comply with the blackmailer's demands. This can happen either if the person has gone to the police or if they haven't. There is only so much that the police can do. Your policy, in place maybe for years, can act to protect someone close to you who is trying to free themselves (as quietly and discreetly as possible) from blackmail.
Further note about blackmail: It is important to remember, that much as we may empathize with a person who has been caught in the blackmail trap, if that person remains in a position in which their official duties are compromised, he or she puts themselves firmly on the side of dishonest, as much as if their compromised decisions were based more directly on illegal financial gain.
Further note about blackmail prevention: If these procedures were standard in our society, the way not opening spam is, it would be much more likely than blackmail attempts would be unsuccessful.