Is the hadith, "May Allah curse the one who divides the community, even if he is in the right," authentic?

There is no hadith with this wording. Dividing the Muslim community is among the major sins that permit the shedding of the divider's blood, as stated in the hadith: "Whoever comes to you while your affair is united upon one man, intending to split your staff and divide your community, then kill him." It is inconceivable for Muslims to unite upon something and then for the truth to be with those who separate from them in matters that do not accept multiplicity. As for matters that do accept multiplicity, such as issues of ijtihad, it is not permissible to divide the Muslim community because of them, even if the person holding the differing opinion is correct, because "disagreement is evil." It is desirable to abandon some recommended acts for the sake of uniting hearts, because the benefit of unity in religion is greater.