Rabbi Yisra’el Salanter had a straightforward answer: “Every sort of neighbour!”
He derives this message from the Biblical text. The opening verse, “Be holy”, tells us to revere those who are able to attain the highest standards.
The second verse, “Respect your father and mother and keep my Sabbaths”, symbolises the intermediate category of people who have not (yet!) reached the really high levels.
The third verse, “Do not turn to idols”, represents the residual category of those who have neither reached high spirituality nor engaged in a basic degree of ethical and religious life, but nonetheless never crosses the line to real idolatry.
Some people are too fussy about whom they love. Others who do not share their commitments or opinions are immediately suspect and not really deserving of tolerance and respect. The Torah, as Rabbi Yisra’el sees it, writes off nobody.