It’s OK to Spit (Beer Faults)
You don’t have to suffer bad beer. Only a tosser would be offended if you spat. Faults in beer are flavours that aren’t meant to be there according to stylish norms. Beauty is in the eye of the beholder. While certain flavours might be seen as great in one beer, they could be a serious brewing faux pas in another. An example would be diacetyl (butter) which is ghastly most of the time but expected and celebrated in Czech Pilsners. Just to clarify butter taste great in food, just not general beer. There are faults though that are faults in no matter what style, such as Lightstruck (3-methyl-2-butene-1-thiol), no matter how fault conditioned the end consumer.
Faults are rather too common in craft beer when really they should never exist. Sometimes owing to inexperience of young craft breweries. Sometimes owing to rushed production schedules. Sometimes owing to inexperience with new recipes or styles and sometimes to care and handling after the beer has left the brewery. Whatever the reason, no faulty beer should ever be released to market and doing so damages the entire industry. If ever you find a fault, never be shy in kindly letting the brewery know. It gives them chance to learn and fix which makes the industry better for all.
Below is a table listing the common flavours considered beer faults sorted by flavour / aroma.