Erasing trees with siege onager is considered a coward thing by the community?

I was on BF, and I was a flank.

They attacked me in 2, my pocket wasn't ready to help so I was left to fight alone and I was the Koreans. Because of the low space I opened the map with siege onagers so that I could fully use all my war wagons... but then one of them called me coward

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btw in the end I won