Reb Moshe was not asked, and therefore did not address where, or whether or not ppl should live.
He was asked whether the woman who live there may or may not carry handguns.
He answered this question.
To infer that reb Moshe held that people should live in a makom sakana is preposterous, disingenuous, inaccurate and halachically unprecedented.
If you interested in R Moshe's shita on the mitzva of yishuv EY you will have to look elsewhere.