I encountered a line in a dictionary in print:
designed to overthrow government: intended or likely to undermine or overthrow a government or other institution
I find the usage of institution in the singular strange. Given that institution is a count noun in this sense, shouldn't it be: government or other institutions or a government or another institution? According to dictionaries, only one meaning of this word takes the form of mass noun, and this usage in the sentence doesn't apply.
When a coordinating conjunction is used (in this case 'or'), we are allowed to omit any word[s] in the second phrase that are a repetition from the equivalent position in the first phrase; thus, "a government or other institution" means "a government or an other institution" ('a' and 'an' are based on the same word, but 'a' is phonetically truncated to precede an upcoming consonant).
When words are compounded, the meaning can change. 'Another' has two meanings, one of which means 'an additional one', so using 'another' could imply that some institution had already been undermined.
Comment: Reading into your sentence, any government that fears being undermined by speech, regardless of the truth in that speech, has already been undermined by its own weakness.
