Free speech is not the right to commit defamation, and politicians are protected by laws banning that as well. For a judge who is really independent, the fact that either the accuser or the defendant may be a politician or even be a president may not be of any importance at all.
Now defamation in sex related cases, is very hard in general. According to jurists who specialized in sexual abuse, proving somebody guilty is hard, but proving innocent is hard as well. For defamation innocence must be proven, yet if Trump believes he has a strong case proving his innocence (charging for defamation when you are guilty even though unproven is very risky), and the money claims you can get on your head should defamation be proven, can be very high, especially when it handles a leader of a nation, and of course, when Trump is no longer president he's still a businessman, and charges like these won't affect his business well, and dang, that could be one hell of a price to pay if that is claimed in money. I personally would not like to risk a defamation charge from somebody in a position like Trump's.
Of course the "fake news" claims on some media coverage, and the ban on TikTok, which is very likely based on some videos ridiculing him (the Dutch news showed them yesterday, they were hillarious) are pathetic. Of course, if those TikTok videos the news showed are the reason behind the ban, we can't speak of defamation (and thus bringing up China spying which is a lot more credible) as that's only a joke. A false accusation of sexual abuse of minors... that's not a joke. That's why I don't wanna compare the TikTok ban to this.
Indeed, if he charges the "victims" (we don't know for sure if they are unless proven, so that's why I use quotes until there is a conviction by court) are indeed false, a defamation suit could be won by Trump, but have political (and business) effects for him that can indeed ruin him even more. The fact that he never denied the claims either, do not prove he's guilty however. It is possible he already has a lawyer on this who advised him not to do anything until the lawyer says so, and although we know Trump is not keep to follow good advice, there's always a chance he did follow it this time. If I were Trump I'd already have spoken to a lawyer about those accusations, to be honest.... But hey, I am not Trump (and happy about that), and I can't read that man's mind....