If you're using the argument that utilitarianism supported gay rights before it was cool to do so, then I feel the need to point out that I skimmed that article, and Bentham says that out of necrophilia, bestiality, homosexuality and masturbation, masturbation is the most damaging to health.

The impropriety then may consist either in making use of an object

1. Of the proper species but at an improper time: for instance, after death.

2. Of an object of the proper species and sex, and at a proper time, but in an improper part.

3. Of an object of the proper species but the wrong sex. This is distinguished from the rest by the name of paederasty.

4. Of a wrong species.

5. In procuring this sensation by one's self without the help of any other sensitive object.

...

Of all irregularities of the venereal appetite, that which is the most incontestably pernicious is one which no legislator seems ever to have made an attempt to punish. I mean the sort of impurity which a person of either sex may be guilty of by themselves. This is often of the most serious consequence to the health and lasting happiness of those who are led to practise it.

You can't just cherry pick his support for gay rights to argue that he supported modern sexual norms 200 years early.