To reject potential tenants before I've met them, based on their Facebook profile?

[GunpowderGelatine]

I'm a private landlord and my flat will be available to rent again next month. Like I always do when I get a new tenant, I've advertised it on a local Facebook page. I've had quite a lot of enquiries, as it's fully furnished and a low price. I've checked out the Facebook profiles of the people enquiring and they include people who have the following on their profiles (I haven't friended any, this is what I can see publicly)

• An intro saying "If you don't like me then simple fuck off"
• A cover picture of a marijuana plant
• Shared memes like the attached

WIBU to say no upfront to these people?

2) marijuana does have medicinal purposes. It used to be legal and was made illegal because well a rich man found a commodity that could be used in similar ways (!not smoked) and set about a swear campaign.
Don't fully understand parts of that, but as a landlord you are deemed partly responsible for what happens at your property, if you are likely to be aware of it. If you had taken in tenants who had a pic if a marauana leaf as a profile pic, and they the police raids and found them running a hydroponics operation, there's a risk that it could appear you knew that was possible.
Personally I wouldn't risk anyone where you can see any hint of anything potentially illegal on Facebook - it's not a court of law, you don't have to have proof that they're doing something wrong, you can choose who you'd want in your property (as long as you don't discriminate on grounds of sex, race, disability etc., obviously).