My dad spanked me? im a 14 yr old girl?

When i was little my parents would spank my bare bottom if i missed behaved alot, but they stopped doing that when i reached about 9, because i was getting older, so they would ground me instead! Well the other day me and my bf Who's 16 were making out on my bed, my dad Walked in on us And at the time my bfs hands were down my pants touching my butt, My dad Roared at my bf and sent him him, He was so angry i had never seen someone so angry in my wjole life He ran back of the stairs to me and closed the Door He told m to take Off my pants And he put me Over his knee He spanked Me Really Hard for about 10 minutes telling me '' i bet you did think you'd have your dads hands on your butt today did you? And if i didnt answer him he'd hit me harder very agresively, i was so scared , and cryin uncontrolably,i didnt expect any of this ,i told my mum when she got home from work and her and dad had a fight their talking now, and im grounded for a month! Does any one think this is just plain wrong or o ye agree with my dad , and think he was right? :(