I have never disliked Stags (except when they play us) probably stems back to the 70s when an old friend of mine Colin Foster played for them. Forest I hated right up to my late 30s but has I've got older I've mellowed and have to admit they are playing well and they don't really bother me any more. Most of my mates are reds fans but they like to see us do well.
That might be different however if we ever got in the same league.