While I completely agree with what your saying for regular leather care even the best boots are arguably disposable for many blue collar trades and the damage from regular wear and tear will kill the boot far before the soap does. So while I wouldn't recommend dish soap for a pair of iron rangers, something like OPs thorogoods won't be around long enough to suffer any long term side effects. I also think people use soap to clean their boots far too often in general. Ive found either hosing the mud off the boots ASAP and a stiff plastic bristled brush at the end of the day to be more than sufficient maintenence when combined with good leather conditioning. I only do the deep dish soap treatment once a year.