I, personally, do not have a problem writing up an aircraft if it deserves it.
However, a couple of cautionary tales...
As a 35 Hr PPL, I was off on my QXC. When taxiing to the hold, I applied the brakes and "felt" something go "ping" through the pedals.

(Sorry but that's the best description I have). So I taxied back and reported in to the engineer. There followed many

a few

and a couple of

. Eventually after taxiing the plane once around the ramp, said engineer pronounced it

.
First land away, I almost came off the runway as the Stbd brakes were almost totally ineffective in the rollout.
Now, I KNEW there was something wrong - even after the engineer had coerced me into taking the aircraft anyway. But I bowed to his greater experience and very nearly came unstuck. It turned out that one of the two bolts which holds the brake caliper together had sheared.
Student 1, Engineer 0.
From that point on, I vowed to have the courage of my convictions, and that was sorely tested about 2 years later.
Now as a fully qualified CPL/IR, I was undertaking my JAA FI instructor course in the US. The aircraft was parked overnight away from base. Upon walking out to the PA28 to do my morning checks before the FIC arrived, I noticed a "creak" coming from the Port wing. It so happened that I had left the brakes on - actually due to my earlier incident 2 years previously, so that I could visually identify a sheared caliper bolt. I'd got as far as the prop and was giving it a good push/pull to check for any play in the crankshaft. The aircraft was, of course, rocking back and forth on the brakes.
Well this creak caught my attention so, of course, I checked the brakes first. But the creak was coming from above, apparently within the wing itself. Curious, I lifted the "gas" cover above the oleo strut on top of the wing and while rocking the plane back and forth, observed slight movement of the gas nipple on top of the oleo. It was very slight but was best observed when referenced against the edge of the hole in the skin where the cover was supposed to fit. The creak apparently corresponded with the location and the small amount of displacement. In turn, this suggested that the oleo appeared to have some movement. Was this normal when rocking on the brakes? I had no idea.
So I called over a friendly engineer from a nearby hangar. He checked both sides. Definate movement in the port side with a creak. No visible movement in the starboard side and no creak.
His opinion was that it needed proper inspection before flight, which meant getting it up on jacks and removing some panels. This, of course, was a problem because the plane was not at it's home base. When the FIC arrived, (15,000 Hrs + experience), he looked at it and pronounced it unsatisfactory also.
Phone call to the flight school, explaining the problem in as much detail as possible. "Fly it back and we'll look at it", was the response. "No way", I said. Eventually, they sent their own engineer - accompanied by a PPL pilot, (not a student). Guess what? Engineer kicks the tyres, say's it's okay and gets the PPL to fly it back to base while HE drives back in the truck.
Next evening, same plane is out on the line ready to be hired.
So, I kick up a fuss. The engineer kicks up a

fuss, going on about his 30 years of engineering experience against my 2 years as a pilot. Threatens to "make sure I never fly at that school again"! The flight school owner tries his best to calm things down and assures me that it will be looked at. However, to make sure... the problem gets "written up". In FAA world, that (should) ground the plane until the engineeer signs it off.
The engineer then says there's nothing to stop him just tearing up the report and binning it!!!

It is worth pointing out that the owner knows absolutely NOTHING about aircraft and depends 100% on his engineer's competance. Since I now have substantial reason to doubt the engineer's competance, accordingly I make discreet enquiries with an FAA Engineering inspector at the local safety center. The FAA inspector promptly calls the owner, and the owner bars me from the school for "shopping them to the FAA". Another FAA inspector then attends the school and inspects the plane.
After all that... the FAA agree that there's nothing wrong with the plane. The engineer is "vindicated" and I am the villain!
Engineer: 10 Student: 1
Moral of the story?
Beats me.