I was driving down the interstate yesterday through some mountains and had a trike motorcycle slam the brakes on and pull to the side of the road suddenly. This happened within about 2 seconds. So in response I put my brakes on, not locking them up or anything, but knowing I had a 4 wheelers a good ways behind me and another big truck passing me. As this driver was passing he had his air horn blaring until he was fully passed. Did I do something wrong, or was he just being a butt?
If you missed the trike, you did fine. Sometimes crap happens, and the only thing you can do is apply the brakes and hope. Don't worry about why he honked, it could be at you, could be at the trike, could be because his butt was itchy. Most likely he missed why you slowed down and got grumpy, but that's not your fault.
Don't let it bother you in any way. Life goes on. Sounds like you made the right decision behind the wheel!