Think what it must be like to be them.
This isn't about you, making comparisons.
This begins with understanding them and their problem . 
If they aren't willing to tell you their problem,
That means that they have already established
That you have a lack of understanding about their problem.
Mental health is what I'm talking about,
Mental health needs to be acknowledged in advance,
So that they feel like they can open up to you.
Without encountering childish remarks behind their backs,
"Mentally disabled" is the wrong terminology for mental health.
This odd person has quite clearly been through a lot.
Whether it's dealing with people judging them,
Struggling to socialize, feeling isolated...
Laughing at them is not positive, in fact,
It's the most negative reaction. No love there.
But what do you love? cars, phones, latest clothes etc...
Their problems are very different to your own.
You need to look up common conditions such as Autism,
To be a better person to those around you,
Because if you don't understand, who else will?