Is returning a gift and shunning a friend due to a feeling of being indebted considered an insult, especially if the friend was the cause of one's religious commitment and boasts about it?

We advise you to resume your relationship with this person who encouraged you towards uprightness and obedience, because it is impermissible for a Muslim to abandon his brother for more than three [days] unless there is a legitimate Shar'i reason, such as him openly committing فسق (flagrant disobedience) or Bid'ah (innovation). If you observe any transgression or offense from him, advise him with gentleness and kindness, and in the best manner. Allah Almighty said: (But whoever pardons and makes reconciliation - his reward is due from Allah), and He, glorified be He, said: (Repel evil with that which is best).