"What hurts about this is the fact that you have a platform to make a difference."
He wasn't done yet. In another tweet, he also told the E! reporter: "You belittle people, rather than try and make people feel accepted and loved, you find things to pick apart like the world isn't full of that already."
Ariana Grande also spoke publicly about the pair's performance.
"We also decided to do this 10 minutes before my set started. we had 0 soundcheck, 0 rehearsal," Grande commented on Bieber's thread. "u were singing with the back tracking like most cameos do. people are bored. people don't know how it feels to be under such scrutiny. the world was happy to have u on stage again."
She added, "i don't like when people try to ruin beautiful moments for my friends that's all. have a good day."
Earlier this week, Stewart said she "did not realise it was going to be that bad", referring to Bieber's performance.
"He definitely looks like he put an oxy pad on that forehead, but I don't care. That is f***ked up!"
Back in March, Bieber opened up about his struggles with mental health.
Stewart has so far not responded to Bieber's tweets.
WHERE TO GET HELP:
If you are worried about your or someone else's mental health, the best place to get help is your GP or local mental health provider. However, if you or someone else is in danger or endangering others, call police immediately on 111.
OR IF YOU NEED TO TALK TO SOMEONE ELSE:
• 0800 543 354 (0800 LIFELINE) or free text 4357 (HELP) (available 24/7)
• https://www.lifeline.org.nz/services/suicide-crisis-helpline
• YOUTHLINE: 0800 376 633
• NEED TO TALK? Free call or text 1737 (available 24/7)
• KIDSLINE: 0800 543 754 (available 24/7)
• WHATSUP: 0800 942 8787 (1pm to 11pm)
• DEPRESSION HELPLINE: 0800 111 757 or TEXT 4202