Forum:Horus LVL 6

Hi there,I am new here. So I was dueling my friend and I used Reasoning,he picked lvl4,but then appeared for summon my Horus Black Flame LVL 6,I summoned him,and my friend told me that I can't because of it's effect,that is unaffected by spell cards,so here I blocked. Is it true?I can't summon him trough spell cards? Please someone help me. Thanks in advance.