While Spider-Man is no stranger to being an object of hatred to both the public and to his fellow heroes, his handling of the events surrounding Scarlet Witch's attack on the Avengers (including the death of the synthezoid Vision) shows why he's perpetually in everyone's bad books.
Wanda and Vision were married way back in Giant Sized Avengers #4. Over the course of their relationship together they faced many ups and down, but through it all remained one of the greatest comic book couples. Their biggest heartbreak came when it was revealed that their twins, Billy and Tommy, were only manifestations of Scarlet Witch’s reality-altering powers. The boys were reabsorbed by the demonic Mephisto, and Agatha Harkness suppressed the memory of them in Wanda, at least until the events of Avengers Disassembled. The crossover event saw Scarlet Witch mercilessly attack her former teammates, who she blamed for the loss of her children, forcing She-Hulk to destroy Vision before eventually being subdued and taken into Magneto's care.
In Avengers #503's 'Avengers Disassembled Part IV,' Spider-Man adds insult to injury. As the assembled heroes discuss whether Wanda can really be behind the chaos, Spider-Man points out that "she married a robot." When the other heroes meet this declaration with disdainful silence, he doubles down by arguing, "If I was dating a robot, you'd all talk about me behind my back." As Norman Osborn once observed, Spider-Man has always been so smart that it makes him dumb, but this poorly timed statement goes beyond that. The tone deaf attempt at humor provokes a backlash, with Falcon asking Spidey why he's even present.
Spider-Man for all his good qualities has always had a lack of impulse control, like the time he threw Wolverine out of a skyscraper. Though his off-the-cuff comments tend to be playful and humorous, they have often made Peter's life more difficult. Many heroes, like Spider-Woman and Red Hulk, genuinely can’t stand him, and a few are downright angered by the web-head’s motormouth. Unfortunately, having developed the habit of running his mouth to soothe his anxiety and distract villains, Spider-Man seemingly can't help himself, making it no wonder that various heroes have expressed a lack of trust towards him in the past.
Ultimately, Peter would be the first to admit that his mouth moves faster than his good sense. His response to Scarlet Witch's attack was insensitive and poorly thought out, and it’s a perfect example of why he’s not always particularly liked by all the Avengers. For better or worse, the one foe Spider-Man will never be able to overcome is his own big mouth.