And seriously, what's the best practice to prevent such cases, when you hold/have access to significant amount of bitcoins?
That's blooming obvious. Do the same as Satoshi, stay anonymous.
Don't make your face, ID, live in public for the criminals to see.
Exactly why you show others that you are using cryptocurrencies. Hide your identity and don't tell anyone regarding your bitcoin activity.
Actually, this is the time to tell about bitcoin to others to promote bitcoin. But we have to give 1st preference to our loved one. Family safety is important.