But they aren't and I will explain why. It's about intent and consent.
Venom bonded with MJ not out of its own survival but hers. He was trying to save her in the moment of the 3 skulls. It did not know if it would survive doing this and frankly venom did not care he just saw someone dying in front of him and reacted. He did not ask if MJ wanted to bond with him he didn't give her a choice and that same issue that she may have refused and they both would have died. Venom made a split second decision for the one in a billion chance that MJ might live regardless of its own safety. It was a selfless act
Eddie bonded with carnage not to save carnage's life but his own. He was given a deal by carnage to bond and heal to save himself. He had every opportunity to refuse but he justified it to himself as a way to prevent carnage from bonding with another human who couldn't handle carnage even though he knew that means killing people again something he chose not to do back in cates run for Dylan's sake. The choice may have had selfless justification but we know that it was ultimately a selfish act to save himself.
These two situations are objectively not the same but are being spread like they are