The full article was posted here earlier today, but his main argument seems to be 'there has been a dramatic continued increase in same-sex sexual experimentation in kids and this makes them bi'.

He continually conflates same-sex behaviour that is caused by purely environmental reasons (prison sex and sex in single-sex militaries, childhood sexual exploration, pederasty, pedophilia etc) with bisexuality. So clearly he rejects the idea that homosexuality, bisexuality and hetrosexuality are all primarily caused by biological determinants and that the people can be forced to act against their sexual orientation because of environmental reasons (such as those listed above).