How do I explain to him that I would much rather work for him, without
looking like a total red flag job hopper.
I'm going to assume you are willing to reneg on your acceptance with Company A in order to pursue a possible job with Company B. And I'm going to assume you don't want to immediately tell Company A that you will not be joining them. (These aren't necessarily choices I would make, but I suspect you wouldn't have posted your question if this wasn't the path you are choosing.)
It will be hard to avoid looking like what you are - someone who already accepted a job and now wants to interview at another company.
Since you believe that the individual at Company B looked at your LinkedIn profile where you announced your acceptance, you obviously cannot hide the fact. Presumably, this person still want to hire someone who just accepted a job - although you probably don't really know the sequence of events here. He may have seen your Company A acceptance before calling you, or after calling you. Either way, honesty is probably the best policy here.
When you interview at Company B, if and only if you are asked about Company A, then indicate that you feel odd about the situation, but that you really want to work at Company B. You might add that you had been hoping to hear from them initially, and perhaps weren't as patient as you should have been.
If asked, you might need to come up with an answer to the question "How can we know that you won't turn right around and quit our company after we make an offer, if you are invited to interview at yet another company?"
Hopefully, you don't have other job-hopping indications in your background.
Of course, should you accept an offer from Company B and quit Company A abruptly, you should expect to burn your bridges with Company A, and everyone there.
And if you are not offered a job at Company B, your willingness to hop from A to B might actually work against you in Company B, in the eyes of different Company B hiring managers. Not everyone at Company B may be as willing to overlook this as the person who read your LinkedIn update and contacted you.
I know this was a dumb move on my part to be a little premature on the
It's a good lesson for the future.