Lets just say, (hypothetically speaking of course) you had a friend who got romantically involved with a drug using money grubbing lying no good fool. What would you do about it?

Nothing...

Try your best to explain that this person isn't healthy (knowing they aren't trying to hear anything you say)...

Or drag them into the woods, tie them up, and beat some sense into them...

Tribbles!!! Howzit?

Nah, I have learned not to interfere.
Unless asked.
Then I will spew it all.

None of your business. Stay out of it....trust me.

no reason to sugar coat it.. tell us how you really feel about this guy.

Personally I have my say but I know they have to make the choice and I don't push the issue. I wouldn't feel right if I kept quiet. My friends speak up to me but they don't push. I'm grateful they speak up

that's a right uppity mirror ya gots there, OP.
best you teach it a lesson and give it a good crack.

First of all if they are my friend then that is what I'm to them... I did not take them to raise I'm their friend.. If they ask me for my opinion I will tell them straight up.. If they use what my opinion is of that person, that is up to them.. If not then I'm still their friend and will be there if all falls apart...

This is the way I treat my family as well and one reason we have the understanding no matter what path they take that is their choice not mine.. As long as they are not hurting me it is really not for me to tell them how to live their lives...

In the end all that matters is we live our lives the way we choose and learn from our own mistakes...

You can tell someone how to live their life, but in reality we learn from the choices we make and deal with...

agree I would keep it shut and let them learn the hard way.not my business what they do in personal love choices

Well I would be a bit more round about, about the topic at hand.
I might throw out a couple feeler questions on doe this person make you happy etc....

By that you will know how to handle this... IF they are crazy over said person it isn't my job to police who my friends date or live with. It is my job as a friend if and when everything goes to hell in a handbasket to be there to help pick up the pieces.

If they stay together then it is my job to support my friend in their decisions.

there is no person more blind than the one who chooses not to see.
you can alert your friend to what's what. there's a high probability they don't want to hear it.
just let that person know they are loved and that you're still their friend

I like the tactics but highly doubt we'll still remain as friends.

Unless I'm asked, I'd stay out of it.

The kind of friend that you wait until they ask for your
opinion? "an aquaintence" Or the kind you ask WTF is going on?
"a friend"

You could tell your friend your opinion but chances are your friend won't listen. It's up to your friend to figure it out unfortunately.