That would only be because they are the only other large party. So for the majority of people/constituencies they are the best alternative if you want to vote to get the Tories out.
All they are doing is comparing the voting at the last general election, polling and then using that two give an option for the best way to vote them out.
Not sure what pro labour facts you think are on there
What do you want about I know constituencies where they recommend the liberal democrats.
The reason it appears to have a Labour bias is that reality has a Labour bias right now. It isn't an unfair bias if it's just reflecting reality, you not like it is immaterial.
I can't see any mention of stopthetories.vote in that discussion though so perhaps it's better than the others, at the very least it appears to give the poll data so there's some transparency there
So your evidence for this is a conspiracy theory on a lib dem subreddit? Do you have any actual evidence that this is a thing that happens because I know for a fact that the website is grassroots is not run by Labour. It's all about holding the Tories to account not getting Labour in.
Edit: OP could not be bothered to provide an answer within 8 hours so I'm going to go ahead and say full of crap.
It’s all about holding the Tories to account not getting Labour in.
Under FPTP there is no way to do one without the other. As others have said. Its a reality bias. FPTP will always lead to a 2 party system. Honestly the current UK system is way better then most. And shows how darn stubborn UK voters can be. As the maths very rarely works for voting outside the 2 largest parties. Without giving an advantage to what each voter considers the larger evil.
The only reason tactical voting sites like this exist. Is to try and minimise the harm 3rd party voting can do to non Tory voters. By informing them of constituencies where those parties are actually likely to win.
People complaining about bias. Truly fail to understand the point of tactical voting. As a non biased system would not need it to prevent spiting of opposition votes.
Yes you can't really do one without doing the other but that point presupposes that you care who the other party is. Lots of people honestly don't. If the Lib Dems were in the position that Labour are in I don't think there would be that much difference in voting intention, except that all the people who intend to vote for Labour would be voting for the Lib Dems except for any constituencies where Labour were more likely to beat a Tory.
People are not voting for Labour because of their revolutionary ideas (unless you count basic competence as revolutionary, and even then it's only theoretical). People who are voting tactically are doing so against the incumbent, not for any particular opposition. They will vote for whichever party has the highest chance of dethroning a sitting Conservative.
Ultimately there is no reason to recommend Labour over any other party unless they were Labor party members. Tactical voting is always against the incumbent, not for anyone. You can't tactically vote for a party, except to just vote for them. But you can tactically vote against a party. So the original accusation that both OP made and in the linked subreddit is both nonsensical and utterly without evidence.