It actually is not an either - or situation .There are two situations . Situation 1 is you are playing against a stronger player . In this case you cannot be merciless and might say it is Ok to lose . On the other hand in situation 2 when you are playing against a weaker player you may be merciless but here you will not say it is ok to lose....
"Some people think if their opponent plays quite well then its OK to lose.
I dont believe this you just have to be merciless" - Magnus Carlsen
In which category do you are?
Its OK to loose
Or
Merciless player
Honestly, i am in first category