Typically, the gods fail to protect those with wrong ideas of them.
That idea comes in with the section that follows the section you quoted:
QuoteOne is not impious who does not take up the gods of the hoi polloi; but the one who attributes the beliefs of the hoi polloi to the gods. [124] For what they believe are not prolepses, but rather the judgements of the hoi polloi concerning the gods which are false, hasty assumptions. So, they believe the greatest evils are brought to the wicked from the gods as well as the greatest aid to the good, because the hoi polloi are believing that the gods accept those who resemble themselves who are similar through all excellences and goodness; all those not of their sort are strange and alien.
For another comparison, here's the Epicurus Wiki which gives an interesting take: http://wiki.epicurism.info/Letter_to_Menoeceus/
QuoteBut do not believe anything about divine nature other than what is congenial for an eternally happy existence. The gods do exist because we have preconceived notions of them. But they are not like how most people describe them, because they do not retain the notion of the gods that they first receive. Rejecting the popular myths does not make one impious. Impious is one who upholds popular beliefs about the gods, because those pronouncements are false opinions rather than actual preconceptions.
And Saint-Andre's:
Letter to Menoikos, by Epicurus
QuoteDo not ascribe to god anything that is inconsistent with immortality and blissfulness; instead, believe about god everything that can support immortality and blissfulness. For gods there are: our knowledge of them is clear. Yet they are not such as most people believe; indeed most people are not even consistent in what they believe. It is not impious to deny the gods that most people believe in, but to ascribe to the gods what most people believe.
Your underlined section in the translations takes into account :
Quoteοὐ γὰρ φυλάττουσιν αὐτοὺς οἵους νοοῦσιν. ἀσεβὴς δὲ οὐχ ὁ τοὺς τῶν πολλῶν θεοὺς ἀναιρῶν, ἀλλ᾽ ὁ τὰς τῶν πολλῶν δόξας θεοῖς προσάπτων.
An even more literal translation of these lines would be:
γὰρ... For, because... (has to be second word in phrase for arcane grammatical reasons)
φυλάττουσιν αὐτοὺς οἵους... they are protecting/defending/maintaining/preserving them (appears to refer to the gods)
οὐ νοοῦσιν they (the hoi polloi) are not perceiving/conceiving/seeing
ἀσεβὴς δὲ οὐχ ὁ τοὺς τῶν πολλῶν θεοὺς ἀναιρῶν "for impiety is not that which is ordained/appointed/taken up by the hoi polloi"
των πολλών is simply the genitive case of 'οι πολλοί (hoi polloi) "the many" which means exactly what it does in English: the masses, the common people. τας δόξας (tas doxas) are the beliefs or doctrines, same word in the Principal Doctrines. So, "One is not impious who does not take up the gods of the hoi polloi; but the one who attributes the beliefs of the hoi polloi to the gods."