But, doesn't the same Bible that shows us this God also reveal and angry and nasty god who told his people to commit genocide so they could acquire the land of Canaan for themselves...?
The Bible's claim is that God is a Trinity of love, revealed by Jesus - from beginning to end. It knows no sense of disunity between the God of the Old Testament and the God of the New Testament. One Bible, one God. No half-time reinvention. No plan B.
When the Bible itself evaluates what we see of God it doesn't say - the OT god is nasty and the NT god is nice. It says, the OT shows the Triune God looking excessively patient, forgiving beyond the bounds of reasonable love. And it's not til the cross of Jesus happens that we have the event that helps us see that abundance of love was truly legitimate.
The same story holds when you look at Jonah's story. Jonah wants Nineveh to burn. He runs because he knows the Triune God wants to lavish his love upon them. People are more nasty than God is. When it comes to Canaan... this is about a patch of land that has been at the centre of controversy for thousands of years. For 400 years it was occupied by the Canaanites, who are a cursed people (Gen 10) who are perpetrators of great evil and child abuse. They're given 400 years in which to turn from their evil - or be judged...
When Israel are set free from their slavery in Egypt they arrive and send out the message that the Canaanites should leave the land. They don't have to die - they just have to get out of the land they've been polluting with their evil. The Bible is more physical than we tend to be - when Israel are booted out for their evil at the end of 2 Chronicles we're told the land breathes a sign of relief. The people of Canaan are invited to join Israel and discover life in the Triune God - there's no exclusivity, all are welcome.
Rahab the prostitute is perhaps the most notable example, joining Israel's royal family and becoming an ancestor of Jesus. They've heard of what the Triune God did in setting his beloved son free from slavery in Egypt - they've heard the gospel and can respond to Christ.
Against those who remain defiant it's the commander of the LORD's army (Jesus?) who leads the army (Joshua 5:15) in against the rebels. The sameone who led his people out of Egypt, who fights for his people and gives himself up for them.
But, should a god of love judge anyone? Might be we ask this because we want to avoid the possibility of ourselves being judged. Whatever our motive, what's a God of love like? The Bible shows us God whose love isn't dispassionate and indifferent to evil. He is no unmoved apathetic deity. His love burns for his own, and against evil, especially evil done against those loved. When evil is done to people, to the LORD's adopted son Israel, to The Son, to the Holy Spirit (who his own people grieved in their grumbling) then his jealous love should rightly burn against evil. We expect justice to be done - and if not don't we then minimise evil and say it doesn't really matter...
If you want a god who is indifferent then you don't want the god of the Bible - but if you want to be cared for by a God who is passionate and warm and giving to his people (and will accept anyone into his people), who is compassionate and pleading and weeping to draw people out of darkness and into his light, and who hates evil with as much passion and he loves his Son, then you're onto someone real, with real love, burning love.