Like lots of people are saying here. Your experience sounds like a combination of rear braking and down changing into corners when things are not matched up properly.
This is all part of the joy and experience of riding big V twins you've got to match the revs when you drop through the gears or the back wheel locks up because it's suddenly geared to go slower than the road speed so it hops and skips. You have to raise the revs by blipping the throttle, (a LOT if you're really dropping two gears at once), or by feathering the clutch on the way out. This is a great way to control back wheel hop and you get a real feel for it. Or you fit a slipper clutch which does this for you, but really it would be better for you to learn the joys of clutch control first. 'cos it's fUN
It's also worth remembering that all this rear wheel fun is also rear wheel engine braking and you have a LOT of this at you disposal also. It's a great advantage on the road and you can learn to ride with this advantage over bikes with engine configurations that don't give them this. Shitty road surfaces, gravel, potholes, wet patches, diesel spills, etc. etc. everytime you see this and need to brake you can opt to not use your front brake and simply whack it down a gear and use that reverse torque and slow without the risk of a front tyre moment.
And last but not least. It's good to get a feel for the back hopping and jumping and sliding and skipping and doing all sorts of strange stuff. The more the merrier. Off road guys have this all the time, it's second nature to them. Keeping it loose and letting the back end have a bit of freedom is maybe OK, you just have to start off by not being scared by it. I try and not be scared of it when it happens rear wheel stuff is usually progressive and you get a bit of warning. And isn't it better to be practiced and familiar with it when it happens?
Front end slides and shit is something else. I don't want to be familiar with them.