隣近所に対して見栄を張るのは人情ですよ。

。

It's human nature to keep up appearances for the neighbors, you know.

Literal

Neighbors [toward-に対して] appearances [object-を] put-up [nominalizer-のは] human-nature [copula-ですよ].

~に対して ('toward, against, in contrast to') marks the direction of an action or attitude. 見栄を張る ('to keep up appearances, put on airs') is a standard idiom: 見栄 ('show, vanity') + を張る ('stretch, put up'). 人情 ('human nature, human feeling') is a cultural concept emphasizing empathy and social obligations.