I have just look for this scene and it's totally...
imprecise? misleading?. It was just the opposite in the comic-books. It could be from
Spider-man #57 (the first time they met, with MJ slapping Ben) or from
Spectacular Spider-man #232 (the second time they met).
Attachment 119701
In the first one, MJ shouts Ben than "no one is going to believe you as him. You're not half the hero he is... Not half the man!". Ben then says: "Mrs. Parker, I can't help the way I look and I can't help but try and help you". She didn't say anything about Ben wanting to take Peter's life. They mention it in the second meeting, but there they were not arguing at all.
Attachment 119702
In the second issue, Ben says "Peter and I were in competition for the same life. That's over. It's taken me a long time... but I've come to terms with who... and what... I am!". MJ then said: "You sound so sincere. I really want to believe you..." to what Ben answers: "I don't blame you for having doubts. It makes perfect sense for me to be jealous of Peter! He's living the ideal live. He has a beautiful wife and family on the way. It's a life I can never have. Clones don't live as long as real people, Mrs. Parker. I came with a degeneration factor. It's only a matter of time before it catches up to me! That's why I'm so eager to help you. At least one of us deservers to live happyly ever after!".
Ben never wanted to take Peter's life away, because he thought he never could have had it. Both issues can be read in
The Amazing Spider-man - The Complete Clone Saga Epic Vol. 3.