Ridge/Liam never wanted to marry people like Quinn or Sheila (General)

That's what makes Carter and Eric pervs and unredeemable creeps. They have all lied, cheated and made mistakes with women. But Ridge and Liam were never paired with bloody serial attempted murderers, kidnappers, rapists. Ridge had so many opportunities to fall for Morgan DeWitt but that never happened. He had a crush for Quinn for a short moment but he came to his senses and forgot all about her. And I could never picture Liam truly falling for a monster like Quinn or Sheila (Steffy is bad in her own way but she is a saint in comparison). Eric married both, knowing what they were capable of. Carter let Quinn manipulate him more than once (the Livy fake wedding, the Vegas fiaso,...) He was horrified when Ridge informed him Quinn and Shauna tricked him. Eric was horrified when he learnt Quinn kidnapped, raped and tried to kill an amnesiac guy, he even joined his family and they all said she belongs in jail. Now both men claim to love her knowing she is still the same manipulative, heartless person (and they don't even know the whole history, like how she spiked Brooke's drink and threatened to kill Donna...)
The day Hope falls in love with Thomas or Liam with Quinn is when I'll officially kick Lope to the curb... and probably be done with B&B for good.

I think I'm done with the show now.

That's what makes Carter and Eric pervs and unredeemable creeps. They have all lied, cheated and made mistakes with women. But Ridge and Liam were never paired with bloody serial attempted murderers, kidnappers, rapists. Ridge had so many opportunities to fall for Morgan DeWitt but that never happened. He had a crush for Quinn for a short moment but he came to his senses and forgot all about her. And I could never picture Liam truly falling for a monster like Quinn or Sheila (Steffy is bad in her own way but she is a saint in comparison). Eric married both, knowing what they were capable of. Carter let Quinn manipulate him more than once (the Livy fake wedding, the Vegas fiaso,...) He was horrified when Ridge informed him Quinn and Shauna tricked him. Eric was horrified when he learnt Quinn kidnapped, raped and tried to kill an amnesiac guy, he even joined his family and they all said she belongs in jail. Now both men claim to love her knowing she is still the same manipulative, heartless person (and they don't even know the whole history, like how she spiked Brooke's drink and threatened to kill Donna...)
The day Hope falls in love with Thomas or Liam with Quinn is when I'll officially kick Lope to the curb... and probably be done with B&B for good.

Don’t think that’ll happen.

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Shown on screen, Steffy blackmailed Bill. Yet, she told Ivy (and Liam too) that “blackmail is a crime”. Per Steffy’s own words, she IS a criminal cuz she has blackmailed.

What is it about Eric that makes him so blindly trusting and easily duped?

I disagree. Taylor and Steffy are as bad as it gets. Murdering lying sociopaths.