Working with farmers nowadays I discuss this one quite a bit with them. All farmers I have spoken to say that they wouldn't go into a field of cows without a big stick to control the cows and whack the cows with if need be.

As to the comment about cows not deliberately being agressive that is misleading. Yes a lot dairy cows tend to be just inquisitive because they are used to being handled twice a day but cows with calves and bullocks can and will be be aggressive even if you're doing everything right. The less they are used to being handled the more likely they are to be aggressive. Just showing confidence can be a start but even farmers have their cattle turn on them sometimes. Hence the stick!!