is this correct?

[spqr]

Propter horum seditiosam atque improbam orationem multitudo frumentum non conferunt quod debent.

" On account of these people by seditious and disloyal argument the common people are not gathering the grain which they should." Assuming my translation is correct a single gender subject with plural verb (multitudo/conferunt in the case) always cause me problems because my first thought is a typo. I know the reasons why a plural verb might be used with a singular subject but how would the intent of the sentence be changed if the subject were plural?

[bedwere]

More text

Unfortunately you are wrong on your assumption. What case goes after propter?
Gender is masculine, feminine, or neuter, not single.
Finally, I don't understand your question, but maybe others will.

[Ronolio]

See AG 317.d.2. It looks like Caesar uses a plural verb with multitudo on occasion. The example they give is B.G.ii.5

cum tanta multitudo lapides conicerent.

As for your translation I would change it to: "On account of the seditious and wicked speech of those (men) the common people are not gathering the grain which they should."