Insecurity is often exposed through criticism, so don't allow the judgement of others to move you. Simply pray for that person because deep down inside their criticism is only a reflection of the insecurity and self-hatred that exist within them. You would be amazed by the many ways a cry for help can be displayed.
“Never return evil for evil or insult for insult (scolding, tongue-lashing, berating), but on the contrary blessing [praying for their welfare, happiness, and protection, and truly pitying and loving them]. For know that to this you have been called, that you may yourselves inherit a blessing [from God–that you may obtain a blessing as heirs, bringing welfare and happiness and protection].”
1 Peter 3:9 AMP