The "Baby" superstar hit out at the allegations on Tuesday, March 26, after becoming riled up by a nasty Instagram comment left on one of his photos of Hailey, who was pictured lounging on a bed wearing a white crop top and thong.
"You are NOT in love with Hailey!" the follower protested. "You only married her to get back at SG (Gomez)..."
The user, who runs an account dedicated to proving the couple's romance is fake, also accused Baldwin of hooking up with singer Shawn Mendes "for fame" and branded her a "racist."
Justin refused to let the rude remark go and responded to the "immature" Internet troll with a lengthy post.
"why would I dedicate my whole life to someone in marriage to get back (at) my ex," he asked. "anyone who believes this is mean spirited or 10 years old or younger because a logical person doesn't talk or think this way u should be ashamed of yourself really (sic)."
Justin claimed he would always have a soft spot for Selena, whom he dated for four years until 2014, and then again for a few months until March 2018, but insisted Hailey is the woman he wants to spend the rest of his life with.
"I absolutely loved and love Selena she will always hold a place in my heart, but I am head over heals (sic) in love with my wife and she is absolutely the BEST THING that has ever happened to me period," he declared.
The 25-year-old then urged other haters to stop harassing Hailey on social media, explaining his rant should serve as a warning to all trolls. "I've seen multiple people say things like this and will never respond again to a message like this because I don't like to even give it my energy but this is a reply to all immature sick people who send Hailey hurtful messages like 'he always goes back to Selena' or 'Selena is better for him' (sic)," he continued.
"YOU HAVE NO IDEA (about) MY LIFE AND WHAts good for me!! Hailey is my Bride period if you don't like that or support that that means you don't support me and if you don't support me your not a fan nor a good person, if you were raised right your parents would have said if you don't have something nice to say don't say anything (sic)."
Justin and Hailey briefly dated in early 2016, but rekindled their romance last June (18), and became engaged in July, before tying the knot in a courthouse ceremony in New York City in September.
The pop star's online outburst came just a day after he announced he would be taking a career break to work through some "deep rooted issues" to become a better husband and future father.