Obviously you do otherwise you would never have made such a post.
I would advise that you grow a back bone, it is your money and your choice nobody else's.
The only person I would listen to in such circumstances is my wife as to a slight degree she can be impacted, but the choice is still ultimately mine.
When you do buy the LS and the next time you are planning to go somewhere with the in-laws make sure you insist that they take their own car as obviously the wouldn't want to be seen going anywhere in a Lexus.