I used to think the same way as you, but a defense lawyer could someday save you from being mistakenly thrown in jail or even sent to the electric chair. A defense lawyer's job is to ensure a prosecutor proves his/her case beyond a shadow of a doubt regardless if the lawyer thinks you are guilty or innocent. Without defense lawyers, there would be many more innocent people in jail or worst, unjustly executed.
A defense attorney is there to protect your constitutional rights.
Yeah, there are scumbags out there. But just because they are scumbags doesn’t mean they don’t have rights.
If we start thinking it is OK to not protect rights based on the accusation, well, the threshhold for the accusation will be lowered.
Reference recent social media giants behaviors in regards to “acceptable speech.”