When you cross a picket line, you undermine the collective action of everyone else who is fighting for their rights
I don't have much regard for anyone who crosses a picket line, regardless of whether they are a member of a union or not. As was pointed out upthread, solidarity matters
Scabs are scum. End of
If you wanted to support the strike action without being on a strike, you could take sick leave, annual leave or unpaid leave
Or you cross it because you have no choice, including not being allowed to take leave.
Calling someone that crosses a picket line a 'scab' without considering why they may have crossed it is infantile. I was called a scab once for doing so - bloody ridiculous, I don't have the right to strike and whether I supported the strikers or not was beside the point. It made me look differently (and pityingly) at the person that called me it - because they obviously didn't understand the industry they chose to work in and were just bandwagon jumping.
Don't make assumptions without knowing the full story.