Just recently I led a seminar for a large engineer consultancy firm. One of my participants had a problem. He tried to reach a client to inform him about a price increase. Because he was scared of driving the customer away, he didn't tell them the reason for his appointment request, yet they obviously had an idea of what it was about and played dead.
In this case "tough on the matter" means not leaving any doubt that there will be a price increase and it's necessary to talk about it. If the client doesn't react on calls they must be informed through a polite email. If they still don't react the increase must be performed regardless. However, in my experience the client will react if they know the matter.
In this special case being "soft to the people" didn't seem a problem. Instead it lacked professional toughness. Meanwhile, I heard that the participant realized the more straightforward Harvard-approach and is really happy with the results.
The issue appears in different constellations over and over again. The mistake most people make is to assume that friendliness equals compliance and toughness means brusqueness. In one of my favorite books "Crucial Conversations"* the authors call this misunderstanding "A Fool's Choice".
It is possible to show and feel understanding for the concerns of the client and at the same time stick to your own interests: "I completely understand that you are not happy with the price increase. And next time I'd rather come with positive news. But for now the adjustment has become necessary and we implement it for all our clients."
Here is how to do it: First, offer understanding. Do this as long as it takes to get a verbal or nonverbal "Yes" from the customer. Then place your message clearly and unmistakably. There can be no doubt that you mean it.
This combination of human understanding and friendliness on the relationship level and clearness on the factual level helps both types of sellers: these who seem to be too nice as well as the seemingly rough ones. Of course, it's a matter of practice because in conflict situations there is also a level of stress involved. But with a little training you will manage to close the gap between both extremes. I promise you will have many great experiences when you try it out.
*"Crucial Conversations" Kerry Patterson, Al Switzler, Joseph Grenny, Ron McMillan - McGraw-Hill, 2002