Our God isn't necessarily the fluffy God most people assume He is. It is a true statement when you say He is love. However, he is JUSTICE and RIGHTEOUSNESS as well. He cannot act contrary to his nature. In Acts, recall the story of the husband and wife who lied about their property. God struck them down right on the spot. Right there, black and white, New Testament. "And we know that God causes everything to work together for the good of those who love God and are called according to his purpose for them." Read into this, it says nothing about doing it for those who do NOT love him.
To expound further, what some people don't understand is that Jesus didn't die to save us from sin. We're guilty of sin, which means we're deserving of God's righteous judgment. Jesus saved us from God. If you do not have Christ as your Savior. You are NOT saved by Grace and you are a sinner in his eyes. Not exactly the fluffy message you are hearing from some pulpits these days.
Think of yourself as a parent, it'd be like your kids misbehaving and deserving grounding or other punishment. Then a Savior stepped in and took the spanking for them out of love. The Savior saved your child from you even though the child deserved it. Of course, multiply that by the depths of infinity and that's what Jesus did for us. Once we realize this, our love for Jesus will increase. He took our punishment, our fine, our spanking that we could never endure. We can never satisfy God's righteous Judgment.
The same God that existed in the Old Testament is the same God that exists now. He does not change. In Revelations, he will pour out His Wrath. Justice is love. Love is justice. You cannot have one without the other. When you wrap your head around that, you'll have the answer to your question.
To take your question a step further, why did God demand the blood that Joshua spilled? Why did Saul and David have war after war? Why did the "Angel of the Lord" kill hundreds of thousands of people? Literally, the OT demanded Israel put to the sword every man, woman, child, and livestock in a particular city.
My personal opinion is we cannot see the details as God sees them. We cannot see into everything, everyone, and everywhere. I'm sure you've heard of the "Butterfly effect." God knows it all. He knows exactly what he is doing and does it with purpose and intent. Even the things that we do outside of His will, He bends to fulfill His purpose and glory as is written in Romans 8:28 again. We have to trust God and have faith that He knows what He is doing. It is written in the Psalms that "His understanding is beyond comprehension." Also Isaiah 55:9, "For just as the heavens are higher than earth, so my ways are higher than your ways, and my thoughts higher than your thoughts."
The conversation on why most Christians still have problems in their life is whole another topic. Just wanna say in short, that all because we're "saved by grace" doesn't mean our life will be perfect. Read about the life of Paul, etc. He wrote 2/3 of the New Testament and to say the least, he had a rough life by our definition.