There is so much written about this topic and there are just as many on one side of the issue as there are on the other side of the issue. If you believe the writings of some, every time a gringo crosses the border, they are shaken down by a TJ cop, or worse. If you believe the writings of others, they've been going down to TJ for 40 years and have never once been bothered by an officer.
Who can you believe?
In the past, I've been very reluctant to write about my experiences because I'm afraid I'll jinx myself. As soon as I say I have never once been accosted, hassled, solicited for a bribe, made to pay a bribe, threatened to be arrested, threatened to be taken to the headquarters, etc., etc., etc. -- of course, then the next three times I venture down for horizontal refreshments, I'll be plucked like a pigeon by some of TJ's finest.
My experiences have been that the officers that I have accosted for directions or information or whatever have always been polite. My Spanish is God-awful but I force myself to try to converse anyway. They try their best not to laugh at my torturing of their language and then answer me slowly in Spanish or else in decent to excellent English.
There will always be crooked cops -- just as there will always be crooked doctors, lawyers, teachers, politicians (especially politicians), bakers, and so on. You may run into one in TJ. You may run into one in San Diego, or London, or Sydney. My condolences if this happens to you. I had a friend once who was beaten severely by San Diego cops. This happened many years ago. It's a long story and although there is absolutely no excuse for what the police did to him, many would say it was his own damned fault. My guess is that some (but not all, of course) of the horror stories you read about the TJ cops are not complete -- you are not hearing what events lead up to the incident or some of the circumstances surrounding the incident were conveniently omitted.
Here is a short story from about a year and a half ago that may be of interest: One early evening, a fellow monger and I were cruising the zone. While he took a chica upstairs in Hong Kong into one of the VIP rooms, I strolled about checking out the SGs. On Constitution, right around the corner from Adelita's, a SG grabbed my hand as I walked by and I coyly kept moving allowing our arms to elongate. A fellow gringo monger was walking toward us from the opposite direction that I was walking. He just happened to reach our outstretched arms as our arms were fully elongated which created something akin to a wall that was blocking his path. It happened so fast that neither the chica nor I were aware of his predicament. It was awkward for him, yes, but his reaction was wholly out-of-line and downright rude. He kept walking in full stride, raised his arms together like a battering ram and used them to break apart our arms. Other than the shock of having a complete stranger treat you so rudely, there was no injury. The chica was more upset than I was and yelled a Spanish epithet I could not understand. I did my best in my horrible Spanish to apologize on behalf of the fellow rude gringo and actually started to think about striking up a conversion / negotiation with the SG.
Within seconds, a TJ police officer who had evidently witnessed the entire event had accosted the fellow gringo and in perfect English ordered him to "assume the position" against the building. He started reading him the riot act, so to speak. I felt a need to vacate the area as quickly as possible so I thanked the SG for her time and moved along. I didn't stick around long enough to determine what happened to the fellow gringo monger.
Now, do you believe the TJ cop's actions were excessive? Was the monger asking to be solicited, harassed, shaken-down, whatever? You decide. But if that monger were to present his side of the story, I'm sure the cop would not be painted in the best light and the rude and obnoxious behavior that the monger exhibited would be left out of the picture.
So, My Brethren, Fear Not the TJ Peace Officer! Follow the advice of our Brother-in-Arms, gfe_seeker: don't get sloppy drunk, don't carry around meds without the prescription, don't flaunt material wealth, etc. Dontcha' Go Lookin' Fer Troubles 'Cause Troubles Might Jest Find Ya'!
Amen.