I would have considered Morris to be a good journalist and she was particularly good at writing about violence against women and girls.
As for her stance in this article, I have some theories:
N Ireland is a conservative society and, despite the ceasefires, still a divided society for a lot of people. One way of signalling that you aren’t conservative or sectarian is to be progressive.
Also, for some from a Nationalist/Republican background, adopting very progressive/liberal politics is a way of showing support for a united Ireland because in the last few decades politics in the Republic of Ireland has become very progressive as a response to a history of social and religious conservatism.
Some political parties in N Ireland have members/politicians who are very religious and as such have a negative attitude towards homosexuality. Liberal people in N Ireland strongly support gay rights and have largely bought into Genderism as being more or less the same thing.
US identity politics ideology also fits in well in societies like ours where people often already view themselves in terms of cultural/religious backgrounds.
As a conservative society, adherence to sex stereotypes is common and in environments like this Genderism blossoms because people who don’t conform to stereotypes see themselves as wrong in some way and are seeking an explanation.