Project Farm gets too much hate IMO. It's just a dude who LOVES tinkering with stuff in his shop and on the farm. It's obvious he's having fun and I think he is truly honest in how he attempts to conduct his experiments and projects. Honest, in that he tries to remove as much bias as possible, even if his tests have no merit to actual tests done by professionals in the field. Members here act if he is doing research for major oil companies and if he does something that's not a valid test his data is going to ruin your engine oil. If he does an oil shootout, and it comes down to two major brands of top-tier engine oil, and one comes out on top, it doesn't matter if his tests were valid for real world use, as a person could have randomly picked any of the reputable oils used in his tests and have a happy engine.
We are all human, and we tend to have expectation when you are trying to give the impression of being accurate and creditable.
For example, if you are a kid doing a video trying to fix a tricycle the viewers will say that's very cute, and don't care if you make mistakes, and they still love you. If you wear a lab coat and do things using "scientific method", but end up being pseudo science, then you bet some viewers will be convinced that you are doing the right way and come out with the right conclusions, and then others, being alarmed, try to correct things (which may not be true either) by raising the concerns, and sometimes trash talk the hosts.
IMO PF could handle it better by thanking the correction and post a follow up video using the suggested method, instead of saying "Hey, this is what I have and I'm not an expert, just trying to have some fun" and brush off the concern / anger / complains. It really makes a difference whether you address the issue or just run away from it.
It is a classic case of the branding does not live up to the expectation.