This story is published in a history that covers reports about the Babi and Bahai religions written by Dutch expatriates in 19th century Iran, and the early history of the Bahai Faith in the Netherlands. It's called "The Babi Question you mentioned" (in reference to one of the Dutch letters written from Iran). The author is Jelle de Vries, who presented it for his PhD in 2002. Our story begins on page 259:.
Before their enrolment in 1954 Mr. A. and Mr. B. Had made no secret of their homosexual relationship – they had in fact told their fellow believers of it – and still the Spiritual Assembly of the Hague as well as the European Teaching Committee had accepted them. But when a year later both were elected into the Spiritual Assembly they could not escape the inevitable clash of personalities. Ands as a ‘struggle for power’ arose they soon were blamed for their way of life. [Source, Van Lith and Sijsling to Regional Spiritual Assembly, 13 Oct 1957]
Matters escalated and the assembly became divided on the issue. Both A. and B. pleaded their case with the European Teaching Committee and the Guardian, as did Jane Boekhoudt, one of their supporters. She received the following answer:
Your letter of September 4th  has been received by the beloved Guardian, and he has instructed me to answer you on his behalf.
Homosexuality is highly condemned and often a great trial and cause of suffering to a person, as a Baha’i. Any individual so afflicted must, through prayer, and any other means, seek to overcome this handicap. But, unless the actions of such individuals are flagrantly immoral, it cannot be a pretext for depriving them of their voting rights.
They young believers in question must adhere to their Faith, and not withdraw from active service, because of the tests they experience. In one way or another we are all tested; and this must strengthen us, not weaken us. The Guardian will pray for these two young believers, and also for you and for the situation there.
With warm Baha’i greetings, R. Rabbani.
At the end of 1956, B. had left the faith, while A. had his voting rights withdrawn. Some member could not accept this situation and openly sided with A. Disunity paralysed the assembly. ... [page 260]
In the following months seven of the believers felt it necessary to retire from Baha’i activity, and by September 1957 the Spiritual Assembly of The Hague could no longer function. [Hollibaugh to RSA, 17 Sept 1957]
That same month the Benelux [Regional] Assembly sent its members Jan Sijsling and Bob van Lith to The Hague to investigate the matter. After meeting several local Baha’is individually they reported to the Regional Spiritual Assembly that ‘the main reasons’ for the problems were ‘personal ambition, neglecting the Baha’i rules for working and living together, [and] authority-problems between pioneer and spiritual assembly.’ As a result the community had split up in three factions, one around Fippie van Duyne, another around A. and a third ‘more or less neutral’ group. In order to rebuild ‘a Baha’i community, which would observe the Baha’i rules’ Sijsling and Van Lith offered to attend the 19-day feasts and assembly meeting of The Hague. [Van Lith and Sijsling to RSA, 13 Oct 1957]
With this external help, which was continued well into 1958, the Spiritual Assembly continued to function. .... It was especially after A. had expressed his intention ‘not to act as a party once he would be accepted again into the Faith,’ and ‘to purify his sexual behaviour,’ thereby enabling the Regional Spiritual Assembly to restore his voting rights in March 1958, that the community recovered. A month later the new local Spiritual Assembly elected A. as its chairman. [Minutes, 8 March 1958] And when B. who had withdrawn from the faith desired to become a Baha’i again, unity seemed to be restored.
One wonders why the subject of homosexuality received so much attention and even resulted in the suspension of voting rights [when other matters such as membership of freemasonry did not attract sanctions...]
The answer consists of at least three components. First the emphasis is only apparently so, for it did not result from the taboo on homosexuality as such, but rather from the impact the matter had on the Hague community. Secondly, [the two Bahais who were freemasons] did not draw attention ... A. and B. on the other hand lived in the same house, and were clearly recognizable to the outside world as a gay couple. Yet, these circumstances can only partly serve as an explanation. There were, after all, other homosexual Bahais at that time who never lost their voting rights. The third and breaking point was that A. and B. defended their lifestyle, tried to win over others to their position, and thereby threatened to cause a split within the community. [Sijsling to De Vries, interview 13 May 1999] In such a situation the Regional Spiritual Assembly could not remain silent, and it therefore eventually had to withdraw their voting rights. Referring to the standard set by the Guardian – ‘unless the actions of such individuals are flagrantly immoral, it cannot be a pretext for depriving them of their voting rights’ – Sijsling (later) somewhat clarified that conclusion by stressing that in general the only criterion for suspending voting rights had been whether or not certain immoral behaviour was ‘flagrant’ or not. [Sijsling to De Vries, letter 7 Dec 1999]
In other words whether or not it was a very obvious expression of disrespect for Baha’i law. Had these two believers admitted their weakness in the face of the Baha’i moral standard, refrained from openly expressing their preference, and not acted as a party it would probably never have come to this sanction.