No — you do not stop being a Jain because someone forcibly made you chew onion.

In Jain dharma, intention and consent matter greatly. If you were forced and did not choose it, then this is not the same as knowingly and willingly eating non-Jain food.

What you should do now:

• Regret any harsh words you said in anger.
• Do pratikraman / repentance.
• Ask forgiveness from the person and from within yourself.
• Resolve to stay calm and avoid retaliation.

So, in simple words:

• Forced eating = not your voluntary fault
• Angry verbal attack = something to repent for
• You are still Jain, but make sure to return to ahimsa, forgiveness, and restraint

If you want, I can also tell you the Jain way to do short pratikraman for this situation.