I am a glutton for punishment but here goes.
I load from a flask to a previously fired "cylinder" all of the time.
I know that it is more dangerous than loading from a scoop. But I do things that reduce the risk to a level I am willing to accept.
If you think it is too dangerous, don't do it.
If you are new to shooting and don't know how to reduce the risk (notice I did not say "eliminate" because there are risks associated with the practice which will always be present) Don't do it.
If you use tobacco products your are placing yourself in danger.
If you ever exceed the speed limit, you are placing yourself in danger.
To be clear:
IT IS MORE DANGEROUS TO LOAD FROM A FLASK WHEN THE CYLINDER HAS BEEN PREVIOUSLY FIRED. KNOW WHAT YOU ARE DOING.
My reading of history convinces me that most bad government results from too much government. Thomas Jefferson