This is a very interesting question that is rather difficult to answer. To summarise my feelings, whilst I think we can identify anger in a large number of the Songs of Experience, I don't think we can say that it is the universal tone of this collection of poems, as some of them focus on other emotions, such as wonder, admiration or confusion.
Let me expand on this brief summary. If we consider a poem such as "The Chimney Sweeper," it is clear that anger can be identified as the predominant tone through the final stanza:
"And because I am happy, and dance and sing,
They think they have done me no injury,
And are gone to praise God and his Priest and King,
Who make up a heaven of our misery."
The bitterness and anger in these last lines, delivered by the poor "thing among the snow," is self-evident as a system comprising of God, priest and king is blamed for the poverty and misery of this chimney sweep. We see anger at such institutional structures that create poverty and suffering throughout many of the poems in Songs of Experience. However, the reason I don't think we are able to state with any certainty that this is a universal characteristic of these poems is that there are a few, like "The Tyger," that do not display any noticeable anger. The speaker instead seems to view the tiger with a mix of wonder, admiration and fear. There is something of the simultaneous attraction toward and repulsion from evil symbolised in the tiger, as the speaker finds the tiger both magnificent and terrifying:
What immortal hand or eye
Could frame they fearful symmetry?
Thus I think we can safely conclude that anger is a feature of many of the poems from this exciting collection, but we should be wary of trying to reduce this challenging selection of poems into any firm categories that would limit their scope and our understanding of them.