I see this objection raised from time to time. But I don't think it's accurate. If there is a UBI I can live off, I'll immediately quit my job at EvilCo doing stuff that I don't believe in or that I find actively harmful. The more evil a corporation is, the more it will have to pay in wages to find someone to do the dirty work. At the same time, the UBI allows people to found startups with much lower risk than today because, if the company does something people believe in, they will be willing to do it for much less money or maybe even for free. (Of course you'll still need startup capital for capital-intensive industries.)
Essentially, the UBI is a subsidy for small business doing socially desired stuff at the expense of big, evil capitalists. I really don't understand why Marxists don't see this and even fear the exact opposite.