The only problem? We've never met in person. My friends keep saying he's a figment of my imagination.

Your friends are right to a certain extent. Until you and your bf meet several times and spend actual time together, you don't really know each other and many gaps are filled by your imagination. It's easy to ignore potential red flags, it's easy to avoid talking about certain topics....

That I shouldn't trust a stranger online ever. I respond that our future as a species is essentially that, trusting software and online mediums.

Yes, you have to trust him to move forward, but you really can't trust someone 100% right from the start when you've never met.