If Tesla is harmed, then mindshare/marketshare/investment can simply migrate to other companies.
You are literally saying that hurting Musk is more important than the fight against global warming. That sends the wrong message. And you would only be willing to send that message if you don't truly believe that climate change is an existential threat.
Nobody complains about how shitty the landlord is when their apartment is on fire, they just get busy putting out the fire and protecting their family and property.
They're already getting that when the leader of Tesla is in bed with the political party that denies climate change. You're also comparing a theoretical harm with an active and ongoing one.
All my arguments hold even if Musk and Trump are the devil incarnate. In fact, they may be the devil that convinces people to take their eye off the ball of climate change. They are exploiting people's emotions and hatred to do damage to the fight against climate change.
It doesn't matter what Musk Tweets, It doesn't matter how shitty Trump is. If you use that as an excuse to do anything less that 100% of what you can to help in the fight against climate change, then you are a climate change denier who doesn't really believe we're in a fight for our lives.