Losing to a guy who I I've seen you talk about frequently as potentially one of the greatest fighters of all time isn't going to destroy Garcia's legacy, whatever people think his legacy may be. Garcia is a very good fighter, but you'd be hard-pressed to find anyone who talks about him as if he's already an all-time great.
I'd rather see Garcia/Lomachenko than Garcia/Spence, but you won't hear me going around claiming Garcia is a duck after taking the considerable risk of fighting a guy like Spence. It's very easy to talk on a forum about how fighting a destroyer like Spence isn't a big deal, but it's not ridiculous at all to say that he is risking his career going forward by taking on this type of challenge. I don't think it's a good idea, but I'm sure as hell not going to talk about him ducking because he wants to follow through with it.