Understanding what words mean is important because, that's the only way that two or more people can understand what one another are saying.
When it comes to the phenomenon of people repeating words without giving definitions, sometimes actually calling bigotry when people ask for definitions, or (and this is rich) claim that you aren't or don't identify with the word that you can't understand it, I think it comes from one of two places - a defense mechanism or conscious manipulation.
If your ideas are shit but you still wanna push them out there, the safest way to do it is to make the most important words that you use to express your ideas as vague and abstract as possible. If your opponents can never clearly understand what the hell you're talking about, they can never clearly prove you wrong. Make everything that you like as wide an umbrella as possible so detractors will always have to admit that there's a form of it that they like. Define "socialism" so broadly as to include the fire department so most people can't find you to be entirely wrong to like socialism (I still can). Define "democracy" broadly enough to include any county that has elections. At the same time, define "fascist" widely enough to include anybody to the right of Bernie Sanders and you've got a go-to accusation whenever somebody disagrees with you.
I do think that a lot of people do this subconsciously. I also do think that a lot of people do this deliberately. Some people are dumb enough to think that the person who is dealing in abstractions, utterly failing to define his or her own words, and insulting an opponent for not understanding the concepts is the smarter person in the discussion. Sometimes a condescending tone of voice and the declaration that the concept is just too complex for the opponent to understand is enough to get others to buy in.
The thing is that most of the great minds in history, most notably George Orwell, warned us about this. The authoritarians like to be pedantic, deal in abstractions, use words with no meaning, because it makes their ideas and actions palatable. Seekers of truth deal in specifics and do what can be done to clarify what is being said.
If you can explain your words in a way that makes sense to a five year-old, that means that you probably have a strong enough grasp of the word to use it. If you can't even define the word for yourself, as many of these people can't, you shouldn't be using the word and you're probably of the authoritarian mindset.
