Unsporting to not berserk when opponent does?

Ladies and gents- is it unsporting to not berserk when an opponent does? This is not a discussion about time management, only whether you consider unsporting to go "full-time" when an opponent berserks?

Can you define "Bersek"?

No, it's not unsporting. Tournaments have set time limits, nobody is giving you away free time when they berserk, they are doing it for the chance to win more points.

It's not.

Its a free choice...