Is the PSL legit?

The most important thing is to join an org that is not tied to or invested in the political fates of either the Republican or Democrat parties. The one thing that should be a deal breaker is when an ostensibly "socialist" party is just a front for Democrat electoralism, as is the case with the DSA. If the party or org you are joining is actively hostile to the duopoly (and not openly reactionary - this goes without saying) then it is good enough. Do not expect perfection, the ideal ideological orientation or 100% correct political line on every single issue.

So long as it is a genuinely independent org and not dominated by Democrat shills there is always the potential for party internal struggle to correct their erroneous lines and weed out problematic behavior. And even if this doesn't happen, it is still better to be a part of a flawed org that does good and useful things to advance the overall struggle than to not be part of an org at all. So i would advise that instead of being hyper-critical and looking for every single bad thing that someone has said about them, you look at what are the good things that they are doing and whether you think you can do some good by being a part of that.

For instance: are they doing community organizing? Are they helping workers organize their workplaces? Are they helping to educate the people and raise the level of class consciousness? Are they speaking out against the imperialists and their warmongering? Are they doing mutual aid or something to protect marginalized communities against reactionary militias and police violence?

Once you join, if you do observe or know of problems within the organization you can try to get together with other members who agree with you and formulate a plan of action on how to raise awareness about these issues and solve them. Ultimately you need to ask yourself who does it really benefit if leftist orgs are examined with a microscope for the slightest imperfection such that people are dissuaded from joining, supporting or even working together with them?

Cointelpro is always looking to cause splits, infighting, to ruin the reputations of the enemies of the bourgeois state and of those who pose a threat to the imperialist agenda, to keep a broad, popular anti-imperialist, anti-capitalist front from forming, to keep our orgs small and divided. Don't fall for it. Criticize leftist orgs that exhibit problems but do it constructively and remember that this is a process, we all learn and get better through struggle.