Yes we need to engage our hearts, in other words use love in our daily lives, and listen to our hearts, our intuition etc, but it isn't true that the mind is the cause of all the worlds woes. The real solution is to keep your head while allowing your heart to grow. "Don't lose your mind/head". The heart is also as much a problem when it comes to the worlds woes. Many atrocities have been committed in the name of love.
Atrocities are also caused by aggression, hate, predudice, greed, vengefulness, pettyness, spite, boredom, jealousy, etc. These are not rational thoughts, a product of "mind", they're emotions - powerful emotions, a reflection of our animal origins. It's through the application of mind that these emotions can be tempered, we can choose to defuse them and not act on them. It's what sets us apart from animals - the ability to think and to choose. Even the decision to act "with love" is a decision that is made by the thinking mind.
In many long-term entrenched conflicts (eg. Northern Ireland, South Africa), resolution has only been achieved by putting these emotions aside, putting in hours and hours on gruelling negotiations, with all sides having to make compromises and learning to live with that. All this requires a lot of hard thinking.
Also, being ethical, having moral values, requires are person to have compassion, which means stepping into someone else's shoes, seeing the situation from their point of view, viewing your own actions from outside yourself. Quite a bit of thought involved in that.
If everyone behaved rationally 100% of the time, there probably wouldn't be any wars. What would be the point? A waste of energy, when you could just talk things over instead...
Being 100% rational would also make human culture a very sterile and lifeless thing, and would not be a society I would want to live in. So yes we need both...
