Transition Dirtbag, Kona Roast 2002 and specialized BMX
Diesel was used back in the day before actual degreasers were any good. My grandad still uses it. Is it right. Probably not. Degreasers are excellent now and while degreasing with diesel may work it isnt the best.
Diesel is the same as #2 fuel oil, aka, heating oil. Kerosene is similar, but slightly more refined. You can use kero in diesel applications, but not the other way around.
IMO, kerosene is cleaner to work with than diesel/#2 fuel. Kero being clear makes it easier to see parts at the bottom of a bowl.
However, disposing of petroleum products is a problem and an environmental no-no, hence the move towards citrus degreasers.
I use kero for parts cleaning. After use I let the crud settle to the bottom of the cleaning basin and the clear kero is poured back into a container for reuse. Only the crud is disposed. This is not environmentally perfect, but it's better than dumping a 1/2 gallon of kero down the kitchen sink.
The use and disposal of solvents are one of "the" environmental issues of our times. If a person is using diesel, it should be properly disposed of, which for the home mechanic is often difficult. There may be waste disposal services offered by your local municipality. Generally, diesel is a poor choice for the personal health of the user, a poor choice for the local environment, and a poor choice for the world environment.
Disposal of so-called biodegradable solvents is often best done down the sink or toilet, assuming you are connected to a modern wastewater treatment facility. Never do this if you are on a septic tank. This is because the treatment facility is capable of handing this type of water, which is basically the same as wastewater from a washing machine. I have seen testing on typical cleaning in the bicycle industry. Generally, we have a fairly clean industry, with very little volatile fluids, and almost none of the heavy metals such as lead, cadmium, or mercury of other industries. Do not add diesel to an otherwise toxic free industry.
Again, it is always best to discuss disposal with your local authorities.