I agree, we spend a lot of time trying to make sure that each target is fair and legal
sometimes we make mistakes, or if the course is set the day before it can become semi obscured quite easily and missed on the pre-shoot inspection.
If a twig or thick grass is obscuring the kill it should be 'called' otherwise that 'Zero' will ruin your day!
We had a few targets with reducers on the rear, infact i made them, i didn't realise the potential problems they can cause...but at certain ranges they certainly can!
Most times you can see that they are reduced by 'wiggling' the target, the majority of hft'ers have come to treat every target with caution as some of the easiest looking targets can be the ones that catch you out
To sum up, in my opinion there will always be the odd shooter that moans, this can be very disheartening for a club that has most probably spent two days with a few guys building and checking their courses, the trick is to be a bit more tolerant of genuine mistakes and not be afraid to ask a marshal if he wouldn't mind moving a twig that obviously shouldn't be there....even if it's a little embarrassing.
That said i have shot 'around' twigs before to save the embarrassment...