It isn't about pissing a user group off...it is all about obeying the rules to make sure access doesn't get compromised (i.e. making sure we don't piss off the folks who control access). Or, causing angina for the guys who've built a good relationship with the park folks (like Shaggz 'n Jorba folk)...
"Illegal" trail work has been an issue at MDR ever since I showed up around here and it still continues today. If it wasn't for the scrambling/efforts/heroics of a few folks out there in mtbnj-land a few years back, we wouldn't be having this conversation as MDR wouldn't be open to bikes. Scrambling still happens when illegal trails, etc., show up.
At the end of the day, would fixing this pipe in an "unauthorized manner" matter? Probably not, but if Shaggz/we can get the green light from the right place, why risk it? Ya' never know when a little bridge can become the straw that broke the camels back.
We may be a little too sensitive to this stuff, I'll admit that. But we've been to the edge and peered into the abyss... Obviously, we'd prefer to stay far away from that and be on our bikes smokin' down Cascade or Stone Gate