When I first saw this sentence, I couldn’t getparse it. When I first saw this sentence, I couldn’t parse it.

I thought there was something wrong, because I misunderstoointerpreted the word “shovelers”,” which I thought meant people. I thought there was something wrong, because I misinterpreted the word “shovelers,” which I thought meant people.

It does actually mean people!

After I gotrealized its meaning, I wanted to analyse its structure. After I realized its meaning, I wanted to analyse its structure.

The “common term" is the subject, “is” is a link verb, “shit shovelers” is predicative, “for pet owners in China” is attributive. The “common term" is the subject, “is” is a link verb, “shit shovelers” is predicative, “for pet owners in China” is attributive.

I don't think "shit shovelers" is a predicative expression, from what I looked up online. "Shoveler" is a noun that means "someone who shovels," like 铲者 I think? Either way some analog of 者 as a suffix. The others look right though.

Then what is the “I think it’s partly because”? Then what is the “I think it’s partly because”?

Well, "because" is a conjunction, so it connects two clauses. You would need the previous sentence in order to fill in the implied parts of the rest of the clause, but it could be like "I think (that the poor perception of pet owners in China is) partly...", and then partly would be an adverb, I think?