Owning Up

My boyfriend recently confessed, owned up to having gay sex with his uncle during his teen years.
He said his uncle would call by knowing my parents would be at their business.
They'd have oral sex, before his uncle would fuck my boyfriend, sometimes more than once.
When he was telling me, I got incredibly turned on and we had sex in his car.
The following day with the vision of his uncle, who I've met lots of times, we had sex again in my bedroom.
When he was inside me, missionary, I slid a wet saliva coated finger up his bum.
I swear he fucked me like never before and I orgasmed multiple times.
Every time since, I've either tongued, fingered his arsehole or both. And each time I get such a thrill from giving him his anal pleasure.
Now I'd like to use a dildo to fuck him with. But he's said his gay past is just that, in the past.
How can I convince him I'd get just as much satisfaction from fucking him, as he obviously would from me sliding a dildo up his bum.
By the way, my boyfriend does have a very sweet and gorgeous looking backside.