The primary school teacher joined the fight for equal rights in Uganda in 1998, when he returned to Africa after the end of apartheid.
He had been the advocacy officer for the gay organisation Sexual Minorities Uganda since 2004 and completed a course on human rights at the University of York last year.
His decision to put himself at the front of the Ugandan equal rights movement came with serious risks and he told supporters he had become more fearful for his safety since his details were published in Rolling Stone magazine.
Mr Kato and two other campaigners successfully sued the newspaper last year, winning an injunction preventing it from outing more gays and lesbians.
The anonymous blogger GayUganda described the first time he met Mr Kato, describing how the activist wanted to be invited to a secret party for gay people.
The blogger said they had given him the wrong address, in case he was not who he said he was, but Mr Kato “used his nose to find where the rest of us were”.
He wrote: “David was a typical Ugandan gay activist. Persistent, in the face of adversity. Ruthless to get what he wants. Patient, when he needs to. A temper that would erupt when he found himself put in a tough situation.”
Another friend, Sokari Ekine, writing for the New Internationalist, said he was “intense and stubborn” and described how homophobia had impacted on his life.
“David had been beaten up many times,” she wrote. “He was constantly harassed and his home was broken into, so he asked for donations to make it secure. A few people sent money but it wasn’t enough. This is no blame time – people do what they can and when they can. It’s just a fact.”
She added that he was in “constant pain” from a dislocated shoulder suffered in a particularly severe beating but was unable to have it attended to by the NHS.
British gay activist Peter Tatchell said: “I salute David and his immense, brave contribution to LGBTI human rights in Uganda. He was an inspiring campaigner of long and great commitment.”
Sexual Minorities Uganda described him as “a dear friend, colleague, teacher, family member and human rights defender” and said his death would not stop their work.
On his Facebook page, Mr Kato had written: “Determined to struggle till a yard done to the journey of liberating the LGBTI community from the discrimination and oppressional laws in the name of sodomy!”
He was killed at his home near Kampala yesterday and was said to have been hit with a hammer.
Reports said this afternoon that a man had been arrested in connection with the death.
Police have apparently said that Mr Kato’s sexual orientation had nothing to do with his attack and that the motive was robbery.
A memorial is to be held for Mr Kato in London. See below for details.
Friday January 28th 2011
10:30am – 12:30pm
Uganda High Commission
58-59 Trafalgar Square
London SW1, United Kingdom
(south side by the start of Pall Mall, nearest tube Charing Cross)