"He looked like a service man THAT was running late for a parade." "He looked like a service man WHO was running late for a parade." Which of the 2 is grammatically correct?
Option 2 is the better option in that there is concordance between the pronoun and the animate personhood of the thing it represents from the prior clause. Option 1 is idiomatically acceptable and common, but I would say it is of a lesser degree of concordance.
Just as a side-note, I find it to be a greater error to apply the pronouns meant for animate persons to inanimate or abstract concepts rather than the other way around. This was a plan whose only aim was to harm the masses. The above example sets my left eye to twitching, though again, it is a commonly seen construction.
"He looked like a service man running late for a parade." No who or that needed in a stylistic sense. Not in fiction anyway.
How else are you supposed to connect it though? Or are you supposed to simply write it differently lol.
For the sake of argument, and to keep that particular piece of syntax in play: This was a plan the only aim of which was to harm the masses. I know that feels stuffy to young readers, but I remain a fan of the of which. Otherwise, yes, a simple reword to remove the need for the pronoun heading a dependent clause. The only aim of this plan was to harm the masses.
I have a guy in my Doctor Who story only talks like that (as opposed to "I have a guy in my Doctor Who story [who] only talks like that") ... Though "who = person, that = thing" is the technically correct.
I've always operated on the basis that 'who' only applies to people. However, I've notice there is some controversy over whether "who" can also can apply to an animal (or a pet) as well. Slightly off topic, but what do you guys think?
"This was a plan to harm the masses." Not a great sentence, but eight one-syllable words are better than nine. Pretty crappy tell too. If masses are going to be harmed, there's a good chance we'll recognize it when it happens.
I've encountered this before—in my own writing and other people's as well—and have been minded to change it. But changing it depersonalised the animal and made it feel like an 'it,' which didn't seem right. I've never been sure. I suspect it's one of those things that will bother some people and not bother others.
