Making fun of "triggers".

Meme: "OMG IM SO OFFENDED."

Its actual meaning(s) mean:

• Gives me crippling anxiety/shakes.
• Makes me want to puke.
  
• Can bring on a slight fever, cold sweats.
• Wanting to scream and run away
  
• Knee-jerk, violent reactions.
  
• Can even spur thoughts of suicide.
  

I'm probably forgetting a few other things, but that's the basics of it.

As well, anything can be a "trigger"... even if it's completely normal to 99.9% of the population. Mine are normal, though I'm not going to mention what they are.
The misinterpretation of abnormal, serious triggers being "silly" is probably how the meme started; people who don't understand picked up on the joke, and it spread like wildfire.

In the end, nobody takes my PTSD seriously anymore; people actively harass me if I even mention it, thinking I'm joking and that I'll become "offended" if they repeat the words over and over again and laugh at the image of me becoming angry.

Nope. I didn't get "offended", I lost my will to live for a few days.
Good job ^/s, you're bullying somebody who has mental trauma... how fucking disgraceful.